EP0073499A1 - Device for indicating the parameters of a dive - Google Patents

Abstract

The device is based on at least one memory containing the decompression parameters of a table of diving depth and times. It estimates and compares measured values of diving depth and times with those contained in the memory. At each moment of the diving, the total climbing time (15) including the imposed decompression stages (16) depending on the duration (13) and on the depth (14) of the diving may be displaced, and/or there is provided a device which transforms, for going to a new depth, the real base time in a time equivalent to this new stage. A single air/water interchangeable pressure sensor is used comprising preferably a piezoresistive cell. LED diodes are lit, if the maximum climbing speed is exceeded (10), if a decompression stage is reached (11) and if the device is out of work (12) by exceeding the time and/or the depth.

Description

• a) wenigstens einen Speicher für die Dekompressionsparameter bei einer Reihe von Tauchtiefen und -zeiten, und
• b) eine Auswerte- und Verknüpfungsstufe für die gemessenen Werte des Tiefen- und des Zeitmessers mit den im Speicher gespeicherten Werten angesteuert ist.

The invention relates to a display device for the parameters of a dive, such as, for example, current depth, maximum depth immersed, previous dive time or the like

• a) at least one memory for the decompression parameters for a series of diving depths and times, and
• b) an evaluation and logic stage for the measured values of the depth gauge and the timepiece is controlled with the values stored in the memory.

When diving with compressed air, the pressure device creates a pressure balance. This means that the air that the diver inhales is under the same pressure as the water surrounding it.

With increasing water depth, the diver breathes air under higher pressure, which causes more air to dissolve in the diver's body. The various gases that make up the air enrich the various tissues of the human body to different degrees according to certain saturation factors.

When it emerges, the opposite happens, the tissues desaturate.

If the ambient pressure drops too rapidly due to the fact that it emerges too quickly, the air dissolved in the blood and tissues cannot be breathed out quickly enough.

In particular, this is the dissolved nitrogen, since the excess of oxygen and carbon dioxide is significantly less. This is because a large part of the oxygen is consumed by the tissues and because of its high rate of diffusion, the carbon dioxide leaves the organism faster than other gases.

If the nitrogen accumulates in excess when the pressure drops too quickly, it can bubble out of its solution to form bubbles. This leads to decompression sicknesses that can be avoided if the nitrogen is allowed to release from the blood and tissues so slowly that there are no gas bubbles.

The disease-causing factor of gas bubble formation is that the nitrogen gas bubbles cause damage in the tissues, that they occur in the blood vessels and get stuck in their end branches, the capillaries. Here they prevent the blood and oxygen supply to the surrounding tissue.

If this state of constipation of a blood vessel (embolism) persists, the affected areas can no longer be fed and perish.

In order to avoid decompression sickness, the diver must not emerge faster than 10 m / min and must take breaks (decompression stops) when the so-called no-stop time is exceeded.

The duration and depth of the decompression stops depends on the tissue saturation of the diver. Tissue saturation in turn is affected by various factors.

• - Maximale Tauchtiefe
• - Tauchzeit
• - Verlauf des Tauchganges
• - Luftdruck an der Wasseroberfläche (Höhe des Tauchortes über dem Meer)
• - Dauer des Aufenthaltes vor dem Tauchgang am Tauchort
• - Vorausgegangene Tauchgänge innerhalb 12 Std.
• - Körperliche Anstrengung unter Wasser
• - Individuelle Gewebezusammensetzung des Tauchers (fettleibig oder athletischer Körperbau)
• - Zusammensetzung des Atemgases.

Without justification and without claim to completeness, here are some of the most important points.

• - Maximum depth
• - diving time
• - course of the dive
• - Air pressure at the water surface (height of the dive site above the sea)
• - Length of stay before the dive at the dive site
• - Previous dives within 12 hours
• - Physical exertion under water
• - Individual tissue composition of the diver (obese or athletic physique)
• - Composition of the breathing gas.

As long as the diver can return to the surface at any time without the risk of decompression sickness, he is at no-stop diving.

Zero time is the time that a diver can stay at a certain depth, so that he does not have to make any decompression stops when surfacing.

For safety reasons, the pressure chamber laboratory at the University of Zurich recommends a minimum stop of 3 minutes at a depth of 3 m for each dive.

Every diver needs to know the ascent conditions in order to be able to emerge without a decompression accident.

These are the ascent rate and the decompression pauses that the diver has to observe during the ascent.

The decompression breaks depend on the duration and depth of the dive and must be spent at certain depths.

Nowadays the diver determines the ascent conditions by hand, with the diver's watch, the depth gauge and the dive table. The determination of the decompression pauses in the dive table is quite simple, but also inaccurate with regard to the optimal decompression, because simple table handling can only be bought with the loss of an exact dive record.

In order to obtain the optimal decompression for every dive, the dive must be recorded exactly and the corresponding decompression conditions must be calculated.

• - Group d'Etudes et de Recherches Sous-marine (Frankreich)
• - Royal Navy (England)
• - U.S. Navy (USA)
• - Druckkammerlabor der Universität Zürich.

It is of course impossible for a diver to do this work himself, because he would have to hold a large amount of data and evaluate it using complicated conversions. That's why recreational and professional divers today use tables from which they can read the decompression conditions. Such recognized tables are, for example, the

• - Group d'Etudes et de Recherches Sous-marine (France)
• - Royal Navy (England)
• - US Navy (USA)
• - Pressure chamber laboratory at the University of Zurich.

These tables are based on experiments with humans and on calculations in which a finite number of tissues with different saturation factors were simulated on a mainframe.

• . Einfache Handhabung
• . Dekompressionsbedingungen für jeglichen Tauchgang mit gerade notwendiger Sicherheit

The diver's requirements for the table are:

• . Easy to use
• . Decompression conditions for any dive with just necessary security

These two requirements conflict with one another because simple table handling requires few table input values, but few input values make an exact recording of the dive impossible. It is therefore impossible to determine the decompression conditions just required for every dive.

All tables are therefore based on the compromise that the few table input values are at the expense of the maximum decompression time and that the diver can only get the decompression that is necessary in extreme cases.

In all other cases, the diver decompresses for far too long.

This means that most of the tables available today are calculated for a straight descent (approx. 30m / min), a stay at a certain depth and for a direct ascent.

The decompression conditions can thus be read from the table by means of the maximum diving depth and the total diving time (time from the beginning of the diving to the beginning of the surfacing).

However, if you compare different tables with each other, you can see that there are considerable differences in the decompression conditions for the same total diving time and the same maximum diving depth.

• - weil die meisten Tabellen für Tauchen auf Meereshöhe ausgelegt sind und das Tauchen in Bergseen nur sehr umständlich, von wetterbedingten Luftdruckschwankungen ganz abgesehen, berücksichtigt wird;
• - weil Tauchgänge, die einem Tauchgang vorausgingen, bei vielen Tabellen gar nicht, bei anderen nur sehr umständlich berücksichtigt werden können;
• - weil die Dekompressionsbedingungen von der Dauer des Aufenthaltes am Tauchplatz und der Höhe des Tauchplatzes über dem Meer abhängen, und dies nicht in allen Tabellen berücksichtigt ist;
• - weil nur sehr wenige Tabellen einen Höhenbereich berücksichtigen, für den die Dekompressionsbedingungen gültig sind;
• - weil den verschiedenen Tabellenwerken ein mehr oder weniger grosser Sicherheitsfaktor beaufschlagt wurde.

This is because:

• - because most tables are designed for diving at sea level and diving in mountain lakes is very cumbersome, not to mention weather-related fluctuations in air pressure;
• - because dives that preceded a dive cannot be taken into account in many tables and can only be taken into account with great difficulty in others;
• - because the decompression conditions depend on the length of stay at the dive site and the height of the dive site above the sea, and this is not taken into account in all tables;
• - because very few tables take into account a height range for which the decompression conditions apply;
• - because the various tables have a more or less large safety factor.

Tables 1 to 4 for 0 - 700 m above sea level and 5 to 8 for 701 - 1500 m above sea level can be found at the end of the description.

• 1. Die Tabellen des Druckkammerlabors sind einzigartig in der Berücksichtigung eines Arbeitsfaktors, d.h. diese Tabellen sind so ausgelegt, dass ein Taucher, der unter Wasser eine körperliche Arbeit verrichtet, ohne Gefahr eines Dekompressionsunfalles nach ihnen dekomprimieren kann.
• 2. Die Tabellen des Druckkammerlabors gehören zu den wenigen Ausnahmen, die nicht für eine fiktive Höhe über Meer, sondern für einen Höhenbereich über Meer ausgelegt sind.

The main differences between the tables in the pressure chamber laboratory at the University of Zurich and all other tables are:

• 1. The tables of the pressure chamber laboratory are unique in the consideration of a work factor, ie these tables are designed so that a diver who does a physical job under water can decompress after them without risk of a decompression accident.
• 2. The tables in the pressure chamber laboratory are among the few exceptions that are not designed for a fictitious height above sea level, but for a height range above sea level.

Since the tables are cumbersome on the one hand and on the other hand require a large number of measurement data, a wide variety of devices and aids were developed for the diver. In addition to different types of depth gauges and diving watches, this is, for example, a decompression meter, which device mimics the gas saturation of the body by pushing gas from a flexible bag through a piece of sintered ceramic into a rigid-walled room. A pressure gauge connected to it shows the pressure in this room. The longer and the deeper you dive with it, the higher the pressure behind the sintered body. The manometer gives the diver approximately information about the progressive saturation of his body tissue.

Since the decompression measuring instruments available today can only reproduce the saturation of human body tissue very imprecisely, this instrument must never be used solely for determining decompression. At the moment this must be determined based on other factors - such as depth and duration - using a decompression table before each dive. The "decometer" can therefore be carried at best for inspection. The reason for this is that decompression meters work according to Boyle-Mariotte's law and can only simulate the influence of nitrogen under increased pressure on the human body. Decompression meters can never work exactly because the gas diffusion through the sintered filter in both directions happens quickly. In the human body (especially with short dives) there are never even conditions. A decompression meter is no guarantee of preventing a decompression accident.

Another common measuring device is the so-called bottom timer. The bottom timer is an automatic dive time measuring device. It is pressure controlled and therefore switches on automatically when a calibrated depth is reached. The bottom timer also switches off shortly before reaching the water surface. It is nothing more than a waterproof "stopwatch", which switches itself on and off by a simple mechanism - pressure-controlled. The bottom timer gives the diver the effective diving time. However, this diving time can also be read on a normal diving watch (adjustable by means of a collar).

Diving time and depth are essential, but not the only factors for determining decompression.

In contrast, a dive computer could record all of the data precisely and evaluate it accordingly. It would be ideal if the dive computer simulates a diver, composed of a finite number of standard tissues. The degree of saturation of the individual tissues as a function of the depth and the saturation factor of the tissue in question would be integrated over time. The decompression conditions could be determined by continuously comparing the critical degree of saturation with the degree of saturation of the individual tissues.

Now there is already a proposal for an ideal decompression meter in analog technology with the help of RC elements Simulation of the degree of saturation of the individual tissues has been proposed. Problems arise, on the one hand, insofar as the degree of saturation cannot be converted into the equivalent decompression conditions; on the other hand, the process of saturating and desaturating the tissues can only be realized to a limited extent using RC elements, because the various tissues have nitrogen half-lives of 5 - 635 have min. This requires extremely large time constants for the RC elements (up to 635 min), which leads to the greatest problems with regard to the dimensioning of the RC elements. Moreover, the proposed analog processing would be far too imprecise for practice. That is why this proposal has never been implemented.

Although various dive computers are already commercially available, little progress has been made because previous dive computers have managed to digitize all the instruments known to date (such as depth gauges, bottom timers, decompression meters). Above all, all known devices have the disadvantage that they only take into account the maximum diving depth and the total diving time as parameters for determining the decompression conditions. This means that after the display of these devices, a diver must comply with the same decompression conditions, regardless of whether he has spent most of the time in shallow depths, perhaps even in a zero time depth and only reached the maximum depth for a short time, or whether he spent the entire dive time in the maximum depth spent.

The result of this inaccurate display is that divers may experience diver times based on actual times and depths showed decompression conditions to make compromises that they themselves only estimate and are thus at risk.

The invention has for its object to enable a more accurate display of the decompression conditions based on the actual diving times and depths. This is achieved according to the invention in that the total ascent time required as a function of the depths and times immersed, including the prescribed decompression stops, and / or a converter device for the current base time when entering a new diving depth level, in this new diving depth level, can be displayed at any time during the dive equivalent basic time is provided.

In order to further increase the accuracy of the display device according to the invention, it is provided according to a further development that the air pressure - preferably measured with the aid of a measuring device - can also be taken into account with the aid of the converter device.

In this way, the air pressure actually present at the dive site can be taken into account, which depends not only on the sea level, but also on the weather conditions. So far, it was only possible to use different, very broadly graduated tables depending on the sea level, whereby the very strongly influencing weather conditions were not taken into account at all.

It would now be conceivable to use two different pressure gauges for measuring the water pressure on the one hand, and for measuring the air pressure on the other hand, but this is preferred provisionally provided that a single pressure meter, preferably having a piezoresistive measuring cell, is connected to the circuit containing the transducer device both for the air and for the water pressure. This not only saves costs for another pressure gauge, it also keeps the device handy, which is especially important for taking it under water.

However, if a single pressure meter is used for pressure measurement above or below water, where the pressure conditions are very different, then either a relatively expensive pressure meter with a wide measuring range would have to be used, or it is expedient that the measuring range of the pressure meter be used for air or can be switched over for water pressure measurement with the aid of a switching device.

The switching device preferably has at least one FET switch, which is followed by an impedance converter for decoupling from the input of the downstream stage, in particular an analog-digital converter.

The converter device itself expediently consists of a computer, and memory (s) for basic times and / or decompression times and / or repetitive groups, which memories e.g. Can be table storage.

In particular, a differentiation stage is connected to the output of the pressure meter because, on the one hand, the ascent rate can be controlled by this stage; on the other hand, it is also possible that the switching device for switching from air to water pressure measurement comprises a step detection step for the pressure, which at is formed, for example, by the differentiation stage.

Other possible designs of this switching device are a manually operated switch (the operation of which could be forgotten, however) or a switch which can be operated by a moisture sensor. However, while the latter version in particular could give rise to incorrect switching during the preparatory shower or when surfacing as a result of residual moisture, the jump detection level ensures safe switching and the same display. The jump detection stage can also be solved differently than by a differentiation stage, for example with the aid of a threshold switch, with memory circuits and corresponding comparison stages or the like.

But also for other reasons, e.g. For a working area limited to an evaluation and logic stage, a range switchover, for example by switching the gain or the bit range of an analog-digital converter upstream of the evaluation and logic stage, can be advantageous with the aid of a switching device. This makes it possible to use cheaper components, such as an evaluation and linkage stage of lower capacity. The switching device can be formed by the same device that also switches the pressure gauge.

Although the switching options listed above for the sake of example are entirely feasible, in some cases they are too complex. In practice, therefore, a solution is preferred in which a reference voltage source that can be switched over by the switching device is preferred is seen, which is conveniently followed by an analog-digital converter.

If, in addition to the water pressure, the actual air pressure is also to be included in the calculation, it is necessary to work with a display device with an arbitrarily, that is to say in particular manually operated, main switch, because the start of operation of the device is automatically not detectable. In this case, it is expedient if, in addition to this main switch, in particular for switching on the pressure gauge, a second switching device for switching further parts of the device when diving into water is additionally provided with the pressure meter. Again, the switching device mentioned above can take on the role of this second switching device in order to save costs for additional components.

On the one hand, every automatic is subject to error possibilities, on the other hand, with reasonable effort, not all possibilities of misconduct of a diver can be recorded. In such cases, the display device may display incorrect displays. However, this would bring an additional danger for the diver. Proceeding from a display device with at least one detector circuit for an abnormal function, such as for malfunction of the diver, it is therefore proposed that a shunt circuit be provided for the converter device and that this shunt circuit can be switched on by the detector circuit, when the abnormal function occurs - for example also when Actuation of the main switch only under water, if the storage capacity or the like is exceeded. - a warning signal through this shunt circuit and / or a drag value display for the maximum reached. Diving depth can be switched on. This ensures that when the capacity is exceeded or another failure of the normal function takes place, at least the display that is available in known devices. In this case, it is particularly advantageous if, in the case of a display device with at least one segment display, it can be alternately switched over to display various display information, for example to the current decompression depth before the abnormal function occurs and to the maximum diving depth afterwards. On the one hand, this saves on components, on the other hand it saves the diver from overloading the equipment, which can only hinder work under water and can also make the display more confusing, and may even give rise to dangerous errors.

To reduce the power consumption of the generally battery-operated display device, it is expedient if an astable multivibrator circuit is provided for clocked activation of at least one display, e.g. 3 to 4 signals per second.

A further increase in the accuracy of the display can be achieved in that the circuit having the converter device also has a memory for the equivalent diving time resulting from repeated diving with the converter device, through any decompression taking account of the decompression parameters and taking account of the surface times of repetitive groups having. Repeated diving and an intermediate stay on the The surface of the diver's tissue may still be saturated with nitrogen as a result of the previous dive, provided this has not already become zero due to a correspondingly long surface stay. In this case one speaks of a "repetitive group zero", which means that the diver can dive without any pre-load. If, on the other hand, the repetitive group is not equal to zero, it can be included in the calculation when diving again in accordance with the above proposal. For this purpose, table memories are preferably provided for the repetitive group tables known per se, but table memories can also be provided for the basic times and the decompression times within the converter device. Such table memories simplify the construction effort. Furthermore, however, it is also expedient if the converter device has a memory circuit for the depths and times immersed in each case and, if appropriate, also for the resulting correction values.

• Die Fig. 1 und 2 zeigen die Diagramme verschiedener Tauchgänge;
• an Hand der Fig. 3 sei die Bedeutung des Luftdruckes erläutert;
• die Fig. 4 und 5 zeigen die Diagramme verschiedener Repetitivtauchgänge;
• Fig. 6 ist ein grobschematisches Blockschaltbild einer erfindungsgemässen Anzeigeeinrichtung, von dem
• Fig. 7 die damit erhältlichen Anzeigen veranschaulicht;
• Fig. 8 stellt hiezu eine Einzelheit des Zeitgebers dar;
• die Fig. 9A, 9B zeigen die Schaltung der erfindungsgemässen Anzeigeeinrichtung, wovon
• Fig. 10 Einzelheiten der Anzeigeansteuerung aus Fig. 9B veranschaulicht;
• Fig. 11 zeigt den dabei verwendeten Code.
• Die Fig. 12 und 13 stellen Alternativen zu einer Schaltungseinzelheit der Fig. 9A dar;
• an Hand der Fig. 14 seien die Hauptprogrammteile für die erfindungsgemässe Anzeigeeinrichtung erläutert;
• Fig. 15 ist ein Speicherbelegungsplan, zu dem die
• Fig. 15A bis 15D die Datenanordnungen darstellen;
• Fig. 16 zeigt die Programm-Struktur, wozu
• die Fig. 17 und 18 Einzelheiten der Programmabläufe veranschaulichen.

Further details of the invention will become apparent from the following description of exemplary embodiments shown schematically in the drawing.

• 1 and 2 show the diagrams of various dives;
• the meaning of air pressure will be explained with reference to FIG. 3;
• Figures 4 and 5 show the diagrams of various repetitive dives;
• 6 is a rough schematic block diagram of a display device according to the invention, of which
• Figure 7 illustrates the displays available therewith;
• Figure 8 shows a detail of the timer;
• 9A, 9B show the circuit of the display device according to the invention, of which
• Fig. 10 illustrates details of the display driver of Fig. 9B;
• 11 shows the code used here.
• Figures 12 and 13 illustrate alternatives to a circuit detail of Figure 9A;
• 14, the main program parts for the display device according to the invention are explained;
• Fig. 15 is a memory map to which the
• Figures 15A to 15D illustrate the data arrangements;
• 16 shows the program structure for what
• 17 and 18 illustrate details of the program sequences.

1A to 1H show different types of dives. According to the previously common tables, decompression conditions must be observed for all dives, which only depend on the maximum depth reached and the total duration. Even if only 38 m were reached during a dive, it would have to be rounded up to 40 m because the tables are only graduated from 5 to 5 meters. Only in the case of a dive according to Fig. 1A would the decompression plan of the tables be fully utilized, i.e. only if you descend very quickly to the maximum depth and remain there until you emerge.

In the example according to FIG. 1B, a stop is made at 19 m during the ascent. According to the tables, this does not count as a decompression stop, but must be added at the dive time. 1A, the decompression conditions are fully used, whereas in the case of FIG. 1B, decompression would have to be decompressed far too long at the expense of the security required for the dive according to FIG. 1A. Of course, most divers are also aware of this, who will then be tempted to arbitrarily shorten the decompression time found in the tables.

) Schweizerische medizinische Wochenschrift 103,Nr.10 (1973)In this regard, it should be mentioned that the complete surfacing tables of the pressure chamber laboratory of the University of Zurich) consisting of five sets of tables of the same structure for sea levels 0 - 700 m (Tables 1 to 4), 701 - 1500 m (Tables 5 - 8), and 1501 to 2000 m, 2001 - 2500 m and 2501 - 3200 m exist and each contain a decompression table, a zero time table, a surface interval table and a time surcharge or repetitive table.

) Swiss Medical Weekly Bulletin 103, No. 10 (1973)

Since the tables are only graduated from 5 to 5 meters, some information about the determination of the "bottom time" or basic time is explained below for the descent phase. It is assumed that no other dive has preceded the previous dive within the last 12 hours. According to the gradation of the tables, the range from a table value for the depth to the next larger table value (whereby the top or first depth level starts at zero m), under "Repetitive dive" a repetitive dive within 12 hours, below "Surface interval time" means the time on the surface between two dives and "current bottom time" means the basic time that is valid until the conversion. As long as the diver is in the first (top) depth level, the bottom time is equal to the total dive time, i.e. the time that has passed since the beginning of the dive.

If the diver dives from the first depth level to the second, it is possible to convert the previous bottom time into an equivalent diving time (bottom time) corresponding to the second depth level. Of course, this only makes sense if this conversion results in a bottom time gain.

This conversion method is based on the fact that when changing the depth level to a greater depth, the previous dive is considered a completed dive, which is now followed by a next dive in the sense of a repetitive dive with zero surface interval time.

This conversion of the bottom time of a depth level into the equivalent bottom time of the next _/ greater depth level can be carried out with each change in depth level from a higher to a lower depth level and is referred to as a gradual descent.

The conversion itself is carried out using the two depth levels and the current bottom time in the time surcharge table.

Examples 1A to 1H: see Tables 9 and 10 at the end of the description, and FIGS. 1A to 1H.

Dives in the range of 0 - 700 m above sea level

FIG. 1A shows a dive with repetitive group zero, as used as the basis for the decompression tables. When surfacing in point e, after a total diving time of 34 min and a maximum depth of 33 m according to Table 1, a decompression stop of 5 min at 6 m and one of 17 min at 3 m must be made.

1B shows a dive with repetitive group zero, in which the surfacing occurs in stages - but within the so-called zero time limit. This no decompression limit (Table 2, or for 701 - 1500 m above sea level, Table 6) specifies the limit values of a dive up to which decompression does not have to take place, ie up to which the diver can do so at any time (of course while observing the maximum ascent rate of 10 m / min) can return to the surface. Now, every previous total dive time in this area can be reached in the equivalent level Dive time of the next depth level can be converted using table 4 (or for 701 - 1500 m above sea level table 8).

The current dive time at one point of the dive is equal to the equivalent dive time of the previous point plus the time that has actually passed since then. If, at this point in the dive, you go down a diving level - or as long as the diver is within the no decompression limits, this current diving time is converted into a new equivalent diving time by first subtracting any repetitive surcharge contained therein, the remaining current one Diving time is converted to the new - always rounded up - diving level and the repetitive surcharge corresponding to this new diving level is added again. As long as the diver is within the no-decompression limit, the conversion is carried out according to the time surcharge or repetitive table (tables 4 and 8), otherwise according to the decompression table (tables 1 and 5).

If rounding errors creep in due to repeated pendulum diving, these are eliminated by comparison with the conversion to the final depth level, if this results in a shorter equivalent diving time.

In the example of FIG. 1B, for point b (15 min, 33 m) in Table 4, rounded up to the table value 17 min at 35 m, the equivalent time value of 19 m (rounded up to 20 m) can be found 34 min. The equivalent dive time is now now 34 min at 20 m. This means that the no-decompression limit has been exceeded (see Table 2) and the prescribed decompression stop according to Table 1 is 7 min at 3 m.

The dive according to FIG. 1C shows a gradual ascent, which however takes place outside the no-decompression limit. In this case, even after the decompression tables of the pressure chamber laboratory of the University of Zurich, no equivalency conversion may be carried out, and it must be decompressed as if the dive had taken place over the entire dive time at the maximum diving depth reached.

1D shows a dive, again with repetitive group zero, in which the diving takes place in stages, but within the no-stop time. As can be seen from Table 5, each time a diving depth level is passed, the conversion into an equivalent diving time can be carried out, which lastly saves a total of 10 minutes diving time compared to conventional calculation, which results in a decompression time gain of even 13 minutes. Theoretically, according to the tables of the pressure chamber laboratory of the University of Zurich, the calculation of the gradual submersion would be allowed, but in practice this has turned out to be far too complicated to make use of this possibility. Only the display device according to the invention has created the possibility of realizing the time savings possible according to the tables.

Finally, Table 1E shows a dive with repetitive group zero, in which the diving takes place gradually, but outside the no-decompression limit. The order The calculation can be carried out in the same way as for gradual descent within no-stop time.

The dives of FIGS. 1A, 1B and 1C end - as indicated in the figures - with the diver being in the repetitive group J. After a surface interval time of e.g. 185 min at 0-700 m above sea level - as can be seen from Table 3 - in repetitive group B; the next smaller time listed in the table must be selected for this determination; Rounding up or down or interpolation are not permitted.

A dive in which the diver dives again with repetitive group B after such a surface interval time is shown in FIG. 1F. After 7 min and 30 m depth, the repetitive group is subjected to the equivalent dive time for the first time and then carried along continuously. After the dive, which actually only lasts 26 minutes, the decompression has to take place as if it had taken 34 minutes.

From dive 1B (repetitive group J) and a subsequent surface interval of 1.50 min, the diver is in repetitive group C. According to FIG. 1G, there is a brief descent to 19 m and a subsequent repetitive dive with gradual ascent. The conventional calculation method would result in the repetitive group D after the ascent in point a and a decompression plan for 75 min at 20 m depth with a total of 18 min decompression stop at 3 m in point e. Now, after very short dives, the repetitive group remains unchanged, always when the line of the repetitive group A in the time allowance or repetitive table is not exceeded. This shows a time of 8 min for 20 m, while the dive according to FIG. 1G only lasted 4 min (not counting the ascent time). In point b, the repetitive group C is taken into account at the diving time 9 min of the new dive with 16 min (from Table 4, at 20 m depth). Because the diver is still within the 18 m depth level at point c, he remains in the no decompression limit, although for the determination of the respective decompression conditions rounded up to 20 m and therefore the no decompression limit would have been exceeded with 30 min. The same applies to point d: the no-stop limit for a depth of 18 m (50 min) has been reached; the diver is at this time in the 12 m depth level, i.e. on an equivalent diving time of 113 min at 12 m and has therefore not yet exceeded the no decompression limit at 12 m at 200 min. The repetitive dive that takes place after the short descent and ascent of FIG. 1G follows the second minute scale, which is recorded under the time abscissa.

Finally, FIG. 1H shows a dive which the diver begins after having been preloaded with repetitive group E from the previous dive 1C and a surface interval of 110 min; the dive consists of a short descent followed by a repetitive dive with pendulum diving. The conventional calculation method would result in the repetitive group F after the ascent beginning in point a and the decompression plan for 72 min at 20 m, ie a decompression stop of 18 min at 3 m in point g. With the converter device according to the invention, however, the - unchanged because repetitive table row A (10 min at 15 m) is not exceeded steps have been taken - Repetitive group E is taken into account in the calculation of the current or equivalent dive time after exceeding the repetitive table line A by the time allowance of 34 min. Diving to the depth of 18 m in point d ultimately results in an equivalent dive time from 37 min to 20 m, while ascending and descending in points e and f allows two different calculation methods. After the first one, the depth is first converted to 12 m, which would give an equivalent diving time of 97 min at 12 m for point f. According to the second, the correction method, the conversion in point e to the depth level of 15 m can be carried out, which means that the entire dive to point f only has an impact of 87 min at 15 m, which means that the diver in point g only has to make a booking Can decompress 5 min at 3 m, whereas it would have taken 10 min according to the former method and even 23 min according to the conventional method.

The conversion with the display device according to the invention results in an equivalent dive time which is less redundant in safety, so that it is worthwhile for the diver to convert if the equivalent dive time is shorter than the current dive time. The respective dive time must also be determined when surfacing, but here the pressure chamber laboratory stipulates that all stops during the surfacing (outside the no-decompression limit) must be added to the dive time in their entire duration, including the ascent time from the maximum diving depth to the stop .

In the following examples (see FIGS. 2A to 2G), “bottom time” means the current, or at most converted (equivalent) base time, “deco” the prescribed decompression conditions.

2 A) dive with repetitive group G after previous dive 1D and subsequent surface interval in the range of 0 - 700 m above sea level of 25 min; Repetitive dive with gradual descent.

Conventional calculation method results in point f and repetitive group G in the decompression plan for 82 min / 85 m: 10 min at 6 m and 38 min at 3 m.

Point a: Gradual descent conversion 17 min / 9 m to 12 min / 12 m; Time saving 5 min.

Point b: Repetitive group G is taken into account in the bottom time calculation after exceeding the repetitive table line A (12 min / 12 m). Bottomtime = 13 min + repetitive surcharge 85 min = 98 min.

Point c: Gradual descent taking into account repetitive group G.

No-decompression limit exceeded (75 min / 15 m) Bottomtime 85 min / -15 m - Deco: 3m / 5min

Point d: Gradual descent taking into account repetitive group G

Bottomtime 64 min / 20 m - Deco: 3m / 18min

Point e: Gradual descent taking into account repetitive group G

Bottomtime 61 min / 25 m - Deco: 6m / 3min and 3m / 30min

• - einem nachfolgenden Oberflächenintervall von 110 min auf 0 - 700 m über Meer - es folgt Repetitivgruppe D aus H,
• - einem darauf folgenden Oberflächenintervall von 80 min auf 701 - 1500 m über Meer - es folgt Repetitivgruppe A aus D.

2 B) Dive to 701 - 1500 m above sea level (see tables 5 to 8!) After previous dive lE and

• - a subsequent surface interval of 110 min at 0 - 700 m above sea level - it follows repetitive group D from H,
• - a subsequent surface interval of 80 min at 701 - 1500 m above sea level - it follows repetitive group A from D.

As a comparison, repetitive group B would arise with a surface interval of 190 min at 0 - 700 m above sea level.

Conventional calculation method in point f and repetitive group A gives the decompression plan for 54 min / 20 m - Deco: 4 m / 5 min 2 m / 19 min

Point a: Repetitive group A is taken into account in the bottom time calculation after exceeding the repetitive table line A (12m / 13min). Bottomtime = 14 min + repetitive time surcharge +13 min = 27 min

Point b: Gradual descent taking into account repetitive group A.

No-decompression limit exceeded (30min / 15m) Bottomtime 41min / 15m - Deco: 2m / 8min

Point c: Gradual descent taking into account repetitive group A.

Bottomtime 34min / 20m -Deco: 4m / 3min and 2m / 9min

2 C) Extreme dive without preload, repetitive group zero, at 0 - 700 m above sea level. Deep dive that exhausts the table values - "out of range".

Point a - h: Gradual descent within no-stop time with maximum time gain of 11 min.

No-stop limit exceeded (Omin / 45m) Bottomtime 5min / 45m - Deco: 3m / 4min

By diving from point a to h too slowly, it would be quite possible that the maximum time gain of 11 min would not be achieved if there was a bottom time of 7 min or 9 min at 45 m, which is reflected in the decompression plan.

Point i: Bottomtime llmin / 45m - Deco: 6m / 2min and 3m / 6min

Point k: Bottomtime 16min / 45m - Deco: 6m / 3min and 3m / llmin

Point 1: conversion 18min / 45m to 16min / 50m; Time saving 2 min; Bottomtime 16min / 50m - Deco: 6m / 5min and 3m / 17min.

Total diving time 27min.

Point m: conversion 18min / 50m to 17min / 55m; Time saved lmin. Bottomtime 17min / 55m - Deco: 12m / lmin, 9m / 4min, 6m / 8min and 3m / 24min.

Total dive time 42 min.

Point n: Bottomtime 21min / 55m - Deco: 12m / 2min, 9m / 7min, 6m / 10min and 3m / 32min. Total diving time 56 min.

Point o: conversion 23min / 55m to 22min / 60m; Time saved 1 min. Bottomtime 22min / 60m - Deco: 15m / 2min, 12m / 2min, 9m / 10min, 6m / 10min and 3m / 35min.

Total diving time 64min.

Point p: conversion 24min / 60m to 23min / 65m; Time saving lmin; Bottomtime 23min / 65m - Deco: 15m / 2min, 12m / 4min, 9m / 10min, 6m / 13min and 3m / 40min.

Total diving time 75 min.

Point q: Bottomtime 26min / 65m - Deco: 18m / 1min, 15m / 2min, 12m / 8min, 9m / 14min, 6m / l8min and 3m / 46min.

Total diving time 95 min.

Point r: bottom time 31min; diving depth 65m; no decompression conditions can be determined for this - table values exhausted. "Out of range" LED lights up, decompression conditions and ascent time are deleted, maximum depth reached is output.

2 D) Extreme dive without preload, repetitive group zero at 0 - 700 m above sea level. Deep dive over 70 m, table values exhausted: "out of range".

• a: Bottomtime Imin xxsec - Deco. für 10min/45m - 3m/4min
• b: Bottomtime Imin xxsec - Deco. für 10min/50m - 3m/5min
• c: Bottomtime Imin xxsec - Deco. für 10min/55m - 9m/lmin 6m/2min
• d: Bottomtime Imin xxsec - Deco. für 10min/60m - 9m/lmin 6m/3min 3m/5min
• e: Bottomtime Imin xxsec - Deco. für 10min/65m -12m/lmin 9m/2min 6m/3min 3m/6min
• Punkt f: Bcttomtime 2min xxsec - Deco.für 5min/70m - 9m/2min 6m/4min 3m/5min Gesamttauchzeit 18min.
• Punkt g: Bottomtime 6min xxsec - Deco.für 10min/70m -12m/2min 9m/3min 6m/4min 3m/6min Gesamttauchzeit 22 min.
• Punkt h: Bottomtime llmin xxsec - Deco.für 15min/70m -12m/2min 9m/3min 6m/10min 3m/20min Gesamttauchzeit 42 min.
• Punkt i: Uebertauchen der 70m Tiefenstufe - LED, out of range leuchtet auf, Auftauchzeit und Dekompressionsbedingungen werden gelöscht, die maximal erreichte Tauchtiefe wird ausgegeben.

Point a - f: From point a there is a continuous increase in the decompression conditions with each dive through the depth levels up to point f.

• a: Bottomtime Imin xxsec - Deco. for 10min / 45m - 3m / 4min
• b: Bottomtime Imin xxsec - Deco. for 10min / 50m - 3m / 5min
• c: Bottomtime Imin xxsec - Deco. for 10min / 55m - 9m / lmin 6m / 2min
• d: Bottomtime Imin xxsec - Deco. for 10min / 60m - 9m / lmin 6m / 3min 3m / 5min
• e: Bottomtime Imin xxsec - Deco. for 10min / 65m -12m / lmin 9m / 2min 6m / 3min 3m / 6min
• Point f: Bcttomtime 2min xxsec - Deco. For 5min / 70m - 9m / 2min 6m / 4min 3m / 5min total diving time 18min.
• Point g: Bottomtime 6min xxsec - Deco. For 10min / 70m -12m / 2min 9m / 3min 6m / 4min 3m / 6min total diving time 22 min.
• Point h: Bottomtime llmin xxsec - Deco. For 15min / 70m -12m / 2min 9m / 3min 6m / 10min 3m / 20min total diving time 42 min.
• Point i: Diving over the 70m depth level - LED, out of range lights up, ascent time and decompression conditions are deleted, the maximum diving depth reached is output.

2 E) Dive with repetitive group zero at mountain altitude 701 - 1500 m above sea level (see tables 5 to 8!).

Realistic pendulum dive.

Point a: Gradual descent conversion 15min / 10m to 13min / 12m; Time gain 2min

Point b: Gradual descent conversion 13min / 12m to 11min / 15m; Time saved Imin

Point c: Gradual descent, conversion from 11min / 15m to 8min / 20m; Time saving 3min

Point d: Gradual descent No-stop limit of the 20 m depth level (15min / 20m) exceeded conversion 15min / 20m to 23min / 15m

Point e: Gradual descent with correction calculation conversion 25min / 15m - 21min / 20m

Correction calculation

Bottom time = bottom time of the depth of 20 m at point d plus the time elapsed since point d.

Bottomtime = 15min + 2min = 17min / 20m no-stop limit (15min / 20m) exceeded Bottomtime 17min / 20m - Deco. For 20min / 20m - 2m / 4min

Point f: Bottomtime 2lmin xxsec - Deco. For 25min / 20m - 2m / 6min

Point g: Gradual immersion conversion 25min / 20m to 20min / 25m Bottomtime 20min / 25m - Deco. For 25min / 25m - 4m / 4min 2m / 8min

Point h: start of the ascent with 10m / min bottomtime 25min xxsec

Point i: leaving the ascending cone, the bottom time is increased by the time spent in the ascending cone.

Bottomtime 26min xxsec - Deco. For 30min / 25m - 7m / 3min 4m / 4min 2m / 9min

2 F) Dive after previous dive 2E and a subsequent surface interval from 70min to 701 - 1500 m above sea level - this is followed by repetitive group D from G - and a subsequent surface interval from 80min to 0 - 700 m above sea level - this is followed by repetitive group B from D .

As a comparison, repetitive group A would be created at a surface interval of 150 min at 701 - 1500 m above sea level.

Conventional calculation method results in point h the decompression plan for 44min / 40m from 12m / 2min 9m / 7min 6m / 20min 3m / 40min,
leaving the decompression phase has not yet been taken into account.

Point a: Repetitive group A is taken into account in the bottom time calculation after exceeding the repetitive table line A (40m / 4min).

Bottomtime = 5 + repetitive time surcharge 4min - 9min

Point b: No-decompression limit (10min / 40m) exceeded conversion 10min / 40m to 10min / 35m

Point c: No-stop limit (15min / 35m) exceeded conversion 15min to 22min / 30m Bottomtime 22min / 30m - Deco. For 25min / 30m - 3m / 5min

Point d: Gradual descent with correction calculation conversion 32min / 30m - 6min repetitive time surcharge A 26min / 30m

Conversion to 22min / 35m repetitive time surcharge + 4min 26min / 35m

Bottomtime 26min / 35m

Correction calculation

Bottomtime = bottomtime at point c at 35m plus the time that has passed since c.

Bottomtime = 15min + 10min = 25min / 35m

Bottomtime 25min / 35m - Deco. For 25min / 35m - 3m / 9min

Point e: Bottomtime 26min xxsec - Deco. For 30min / 35m - 3m / 12min

Point f: Bottomtime 3lmin xxsec - Deco. For 35min / 35m - 6m / 5min 3m / 17min

Point g: Bottomtime 36min xxsec - Deco. For 40min / 35m - 6m / 7min 3m / 20min

Point h: start of the ascent to decompression at 10 m / min

Point i: During the decompression phase, submerge more than 3 m below the lowest decompression level (7m).

All of the previously decompressed time is applied to the bottom time.

Ie: Bottomtime = 40min + 5min decompression time = 45min

Bottomtime 45min / 35m - Deco. For 50min / 35m - 9m / 3min 6m / 10min 3m / 35min

Point k: Start of decompression again, but now for 50min / 35m.

• 1. Tauchgang mit Notaufstieg
• 2. Tauchgang, wobei der Tauchcomputer erst unter Wasser eingeschaltet wird.
• • 1. Punkt a: Nullzeitgrenze (Omin/45m) überschritten Bottomtime 2min xxsec - Deco.für 10min/45m - 3m/4min
  • Punkt b: Notaufstieg-Beginn
  • Punkt c: Eintritt in die Dekompressionsstufe, LED - DECO leuchtet auf.
  • Punkt d: Eintritt in die Oberfläche ohne den vorgeschriebenen Dekompressionsstop einzuschalten. LED"-out of range^Hleuchtet auf. Dekompressionsbedingungen, Auftauchzeit und LED - Deco werden gelöscht, die maximal erreichte Tauchtiefe wird ausgegeben.
• 2. Punkt a: Einschalten des Tauchcomputers unter Wasser - LED, out of range"leuchtet auf, maximal erreichte Tauchtiefe wird als Schleppwertanzeige ausgegeben.

2 G) Extreme dive without preload, repetitive group zero at 0 - 700 m above sea level.

• 1st dive with emergency ascent
• 2nd dive, whereby the dive computer is only switched on under water.
• • 1. Point a: No-stop limit (Omin / 45m) exceeded Bottomtime 2min xxsec - Deco. For 10min / 45m - 3m / 4min
  • Point b: start of the emergency ascent
  • Point c: Entry into the decompression stage, LED - DECO lights up.
  • Point d: Entry into the surface without switching on the prescribed decompression stop. LED "-out of range ^H lights up. Decompression conditions, ascent time and LED deco are deleted, the maximum depth reached is output.
• 2. Point a: Switching on the dive computer under water - LED, out of range "lights up, the maximum depth reached is displayed as a drag value display.

In any case, it is essential that every diver who stays above the no-decompression curve with regard to the diving time and the maximum diving depth is in the area of the no-decompression diving and therefore does not have to make any decompression stops when surfacing (although a break of 3 min at 3 m depth when surfacing is recommended becomes). However, as long as the diver is within the no-stop time, the procedure for determining the equivalent basic time described above with the aid of diving can also be applied to the surfacing, because the diver can emerge again at any time without decompression.

Under these conditions, you can also provide a time allowance for the subsequent dive from the time allowance table when surfacing (in the sense of a repetitive dive). The problem now arises, however, that if this method is generally used for all depth levels and if the current base time is converted if the depth level is exceeded upwards into the base time of the higher depth level, considerable rounding errors will be introduced, which will be particularly noticeable if the diver only takes a few Depth levels swim up and then dive back down to the maximum depth level. The solution to this problem advantageously consists in the fact that the previous diving at a greater depth is only converted to the depth level of the current diving depth if the current base time

just got as big as the no-stop time of the maximum diving depth. When converting the base time to the current diving depth, only one correction time needs to be recorded and the previous base time used as the correction base time. However, these two correction values are only required if the diver returns to the maximum depth level within a short time.

It is then necessary to compare whether the sum of the correction bottom time and the correction base time stopped at the time of return is smaller than the current bottom time that has elapsed up to this point. If so, the current bottom time must be corrected by setting the sum of the correction bottom time and correction time. Otherwise the conversion was worth it.

This new method gives a significant advantage, because it makes it possible to assemble a dive both in the dive and in the dive to a certain extent from successive repetitive dives according to the tables, thereby creating the conditions for digitization.

The digitization of the dive was given so much attention because the values required to determine the decompression conditions, the bottom time and the maximum depth can be determined optimally. The procedure is as follows. The associated decompression conditions are read in the decompression table with the bottom time and the maximum diving depth.

Decompression conditions are the decompression times of the individual decompression stages in the decompression table, which times the diver has to observe.

The existing regulations are somewhat different if a dive is preceded by another dive within 12 hours. As already explained with the help of the above conversion examples, each dive is assigned a repetitive group at the beginning of the surface interval, which corresponds to the degree of saturation of nitrogen in the diver's tissue, in order to determine a corresponding surcharge for the decompression parameters. Conventionally, at the beginning of the repetitive dive, the repetitive group is determined for the end of the surface interval.

However, it is advantageous if, in contrast to this conventional method, the repetitive group is continuously updated during the surface interval in order to shorten the surface interval table required for this and ultimately to save storage space for the display device according to the invention. The result, i.e. the repetitive group resulting at the end of the surface interval is the same. The continuous determination of the repetitive group will be described later with the explanation of the program sequences.

Usually, the repetitive group is only taken into account at the beginning of the surfacing, because if you look at the table, the conversion of the base time would have to take into account the repetitive group. Becomes but, as is done according to the invention, if a corresponding converter device is provided, the corresponding correction can easily be carried out independently.

It is therefore expedient if the repetitive group is taken into account at the end of the surface interval for each depth level change during the descent by a repetitive time surcharge. This gives the possibility to indicate the minimum ascent time including the decompression time to the diver at any time. In the conventional method, the decompression times increase suddenly at the beginning of the surfacing, i.e. the correction would be significantly more complicated because corrections have to be made anyway when determining the base time (according to the explanations above) and an additional correction value only creates additional complications.

If the base time when diving is to be converted taking into account the repetitive group, the repetitive surcharge of the previous change in depth level is subtracted from the current base time before converting the current base time, then the conversion is carried out in the manner described above and finally the repetitive time addition of each next lower depth level added to the current base time. This means that the previous dive and its resulting preload on the tissue are superimposed on the values of the dive each time the depth level is changed. According to the description above, these values can already be in digitized form.

With reference to FIG. 3, it will now be explained which problems arise in connection with the consideration of the air pressure. Assuming the same temperature at the different altitudes, the air pressure decreases with increasing altitude according to an exponential function. When calculating the air pressure accurately, it must be taken into account that the temperature decreases with altitude. In order to get an accurate picture of the air pressure up to an altitude of 4000 m, it is calculated according to the international altitude formula, which takes into account an annual mean temperature at sea level of 15 ° C and the air pressure in the annual mean at sea level of P _o = 101.325 kPa . It is valid up to a height of 11,000 m and is

Um ein möglichst realistisches Bild der Luftdruckkurve zu erhalten, müssen die wetterbedingten Luftdruckschwankungen berücksichtigt werden, welche als Folge von Wetterstürzen auftreten und auf Meereshöhe bis zu + 50 mbar ausmachen können. Das sind 5 % relativer Fehler, der der Luftdruckkurve als Streubereich überlagert wird.

In order to obtain a realistic picture of the air pressure curve, the weather-related fluctuations in air pressure must be taken into account, which occur as a result of sudden falls in the weather and can amount to up to + 50 mbar at sea level. This is 5% relative error, which is superimposed on the air pressure curve as a range.

The air pressure curve shown in FIG. 3 is approximated by means of a straight line 4 through the points (0/1) and (3300 / 0.67), where ΔL is the maximum change in air pressure at sea level and S is the scattering range of the air pressure fluctuations, which makes up about 5%. Located further relates to the Altimeter resolution A m per 100, the maximum error F _M of H _ö henmessers, as well as the minimum error F _Smin and the maximum error F _Smax of the measured via the air pressure level in the region of the transition from a high level in the other can lead to the selection of the next table set.

This shows that the 5% relative error in air pressure results in a significantly larger relative error in altitude.

When considering the individual height level limits (700/701, 1500/1501, etc.), the relative error increases to a maximum of + 72% (-500 m to 700 m), and remains at a minimum above 10% (+ 350 m to 3200 m).

These enormously large deviations of the cartographic height from the sea from the air pressure level are considered in the tables of the pressure chamber laboratory of the University of Zurich with safety factors, so that the diver is not endangered.

Example:

According to the map, a diver is at a mountain lake at 1300 m above sea level and uses the table set for the altitude level (700/1500) m above sea level for his dive. However, the prevailing air pressure may have risen so much as a result of a sudden fall in the weather that it now corresponds to an equivalent height of less than 700 m above sea level. Now the diver could use the table set of the altitude level 0-700 m above sea level if he used an altimeter instead of the map to select the table set.

A precision altimeter is not required to achieve greater accuracy in the selection of the table set than with the aid of a map. The relative error of this altimeter only has to be smaller than the minimum relative error of the cartographic altitude in relation to the height equivalent to air pressure. The relative error of the altimeter therefore only needs to be less than 10%. The display device according to the invention takes sufficient account of the air pressure and therefore, under the conditions of the example mentioned, correctly accesses the table set 0 - 700 m above sea level, which corresponds to the prevailing air pressure, even though the diver is at 1300 m above sea level.

On the other hand, the following applies to the pressure (P _w ) of the water column:

H₂O = 10³ kg/ m³ so gilt:Assumption (P _w ) = bar and

H ₂ O = 10 ³ kg / m ^{3 the} following applies:

(2) diving depth in meters = 10 P _w

Because the water depth cannot be determined independently of the prevailing air pressure (P _h ), this must be taken into account. The water pressure (P _w ) is the difference between absolute pressure (P _abs ) and air pressure (P _h ). It therefore applies to the diving depth (DEPTH) in meters and the pressures (P _abs ), (P _h ) in bar:

(3) DEPTH = 10. (P _from s - Ph)

In order to determine the diving depth when diving at different heights above sea level, an absolute pressure sensor must be selected and the diving depth calculated according to (3).

= 1,0 g/cm3.The specific weight of sea water is approx. Y = 1.025 g / cm ³ , that of fresh water approx.

= 1.0 g / cm3.

Because the diving depth has to be determined in both sea and fresh water, a short error analysis follows.

If the actual diving depth is determined according to (3), taking g into account, at an actual diving depth of 10 m, then the diving depth in fresh water is 10 m, and the diving depth in sea water is 10.25 m. The relative error of the depth in the sea water with respect to the real depth is + 2.5%. This accuracy can be used, especially since the error is on the safe side and therefore the depth is never determined too low.

This results in the specific requirements for a pressure measuring system as used according to a preferred embodiment of the display device described later, namely for an absolute value pressure sensor of 0-10 bar, so that the height range 0-4000 m above sea level and the water depth range 0-80 m can be detected.

The relative error must not exceed 3.5% in order to be able to guarantee a sufficiently high accuracy of the height measurement and depth measurement.

The sensitivity (E ₌ V must be so great that a pressure change of 0.01 bar = 100 m air column = 10 cm water column results in a voltage change which after amplification and A / D conversion digitally has at least one digit of the lowest value is represented as a binary value (E) ₂ ≥ (1) ₂ .

It has already been mentioned that repetitive dives within 12 hours must be taken into account when determining the decompression parameters. This will be discussed in more detail below. It has also already been said that the various repetitive groups are designated by letters and lead to a time surcharge according to the time surcharge table.

4 shows the graphical representation of a repetitive dive with a dive time T ₂ after a previous dive with a dive time T ₁ and a decompression time D and after a surface interval Oi. For example, the diving time T _{1 is} 50 minutes and the decompression time D is 3 minutes on the basis of this diving time and the depth (10 m), which results in a repetitive group F after surfacing and at the beginning of the surface interval. 4, the surface interval Oi is 100 min. The excess gas content in the body of the diver decreases and a repetitive group C occurs, which corresponds to a smaller amount of gas. This can be found in the surface interval table. The diver, who is now in repetitive group C, wants to dive to 30 m. In the C line of the time surcharge table, he finds the time surcharge of 10 minutes in the 30 m column. This means that there is still as much gas in the diver's body as if he had been at 30 m for 10 minutes. To determine an appropriate decompression, the time surcharge must now be added to the new, real diving time. If the real diving time is now 20 minutes, for example, he must select the decompression plan for 30 minutes at 30 m.

A repetitive dive according to FIG. 4 at constant sea level is now the most common case. But what happens when the diver changes water and sea level is discussed with reference to FIG. 5.

At higher altitudes, the times with which a certain repetitive group is reached are shorter. It is permitted to calculate the surface interval in height using a lower table set; the reverse, however, is not permitted.

Example according to FIG. 5

1st dive 450 m above sea level, 40 min at 30 m; after the prescribed decompression under water, the diver is out of the water at 11.01 a.m. and is now in group J. With a helicopter, he is now flown to a mountain lake at 1400 m above sea level. At 12 noon he exceeded 700 m above sea level. At this point, he is in Group G, which allows him to fly up to 2000 m above sea level. At 12.55 p.m. he is ready for the new dive. According to the surface interval table 0 - 700 m above sea level, he was in group F from 12.06 p.m. The remaining 49 min surface interval time is taken into account in table set 701 - 1500 m above sea level and comes from group F at 12.55 p.m. Group D. According to his new diving depth, he now looks for the time allowance. The dive ends at 1.30 p.m. and he is now in Group G. At 3.10 p.m. he drops below the altitude limit of 700 m above sea level.

In the table set 701 - 1500 m above sea level, it was in group C after a surface interval of 90 min (ie at 3 p.m.). The further surface interval after 3 p.m. is taken into account in the table set 0 - 700 m above sea level, since the surface interval table 701 - 1500 m above sea level is no longer valid if the limit is below 700 m above sea level.

• Die obigen Ausführungen zeigen, dass die Handhabung der Tabellen verhältnismässig umständlich ist und es daher unmöglich ist, damit dem Taucher zu jedem Zeitpunkt eines Tauchganges diejenigen Informationen zu geben, die er eigentlich nötig hätte. Die bisher bekannten Tauchcomputer haben das Ablesen der Tabellen lediglich automatisiert, ohne dabei eine Umrechnung der aktuellen in die äquivalente Grundzeit, eine Einbeziehung des tatsächlichen Luftdruckes (der gemäss Fig. 3 erheblichen Schwankungen ausgesetzt sein kann) bzw. der Repetitivzeitzuschläge, oder eine laufende Anzeige der jeweils erforderlichen Auftauchzeit zu ermöglichen. Insgesamt waren also die von ihnen erhältlichen Angaben mit grossen Ungenauigkeiten behaftet. Hier Abhilfe zu schaffen und dem Taucher eine möglichst genaue Information, insbesondere über die Dekompressionsparameter, zu vermitteln_tist Ziel der Erfindung.

Structure of the display device according to the invention:

• The above explanations show that the handling of the tables is relatively cumbersome and it is therefore impossible to provide the diver with the information that he actually needed at any time during a dive. The previously known dive computers have only automated the reading of the tables without converting the current to the equivalent basic time, including the actual air pressure (which can be subject to considerable fluctuations according to FIG. 3) or the repetitive time surcharges, or a continuous display of the to enable each required ascent time. All in all, the information they received was associated with great inaccuracies. Here to remedy the situation and to give the divers the most accurate information, especially about the Dekompressionsparameter, _t is the aim of the invention.

Fig. 6 shows an embodiment by means of which this goal can be achieved. The ambient pressure (ie both air and water pressure) is supplied to at least one pressure meter 6 as an input variable to a converter device 5. A further input variable is provided by a timer 7, which - as will become apparent from the description below - can also be integrated in the converter device. Finally, there has to be one Voltage supply circuit 8 can be provided, which can be switched on via a main switch 9 which can be operated arbitrarily, ie directly manually or at most via a remote control.

Not only the start and end of a dive and its course are recorded within the converter device 5, but preferably also the previous history, so that the repetitive time surcharges can be taken into account. For this purpose, it is of course necessary that the converter device 5 itself and / or storage devices connected to it receive the associated table material. The signals are expediently processed in digitized form, which is why it will be necessary, at least for the pressure meter 6 that supplies the analog signals, to provide an analog / digital converter within the converter device 5.

A starting value At for the expected surfacing time (including the decompression time), the decompression parameters D (ie depth levels and times for the decompression), the depth information Tm (such as the current depth and maximum depth) and the total diving time can be used as the output variables of such a converter device 5 Determine Tt. Furthermore, it is also expedient if abnormal functions are displayed, ie faulty behavior of the diver and / or the display device itself. Thus, a display Va for exceeding the maximum ascent rate of the diver and at least one further display An can be provided, which indicate a battery monitoring signal inadequate energy supply and / or a signal if values occur that do not appear in the stored tables, for example because the diver is in too has casually exceeded the maximum depth of 70 m.

Although the display device must of course be accommodated in a pressure-proof housing, a leak sensor with a corresponding display can also be provided. Furthermore, the display device must be captively attachable to the body of the diver, expediently on the arm, but in the event of a loss (for example when removing the device because the device interferes with work under water), it can include a motion detector which, in the absence of one, of After a short period of time, divers cause an optical, acoustic and / or other targetable signal to facilitate retrieval.

When the display On responds to indicate that the end of the table has been reached, the decompression parameters (output variables D) can no longer be determined exactly. It will be explained later that in this case a shunt to the actual converter device can be provided, by means of which shunt circuit the current diving depth and the diving time are displayed to the diver, but the decompression conditions and the ascending time are deleted, because the latter result from the abnormal behavior of the Divers can no longer be charged. For example, in the event of an emergency ascent without complying with the prescribed decompression stop, in order not to leave the diver completely without information, the maximum diving depth reached is also displayed so that he can determine a decompression plan for himself using the diving time and the maximum diving depth achieved after self-improvisation.

Overall, an embodiment of the display device according to the invention is expediently designed such that the diver only has to switch it on or off by means of the main switch 9 - before entering the water 1. The device then works fully automatically and its operation is reduced to observing the display. The diver will appreciate this simplicity of handling because the diver's ability to concentrate is anesthetized with increasing depth and his dizziness increases. In extreme cases, anesthesia can turn into a deep intoxication, which has been a fatal fate for many divers. It is therefore all the more important to have an easily readable and understandable display in which only those values are shown that the diver really needs.

• - sich an Land oder im Wasser befindet;
• - an der Wasseroberfläche schwimmt;
• - am Abtauchen ist;
• - vorschriftsgemäss auftaucht,
• - schneller als mit l0m/min auftaucht,
• - zu langsam auftaucht;
• - ohne oder mit Vorbelastung aus vorangegangenen Tauchgängen taucht;
• - die abzuarbeitende Tabelle in ihren Werten überschreitet;
• - die Nullzeitgrenze überschritten hat;
• - dekomprimieren muss;
• - die Dekompression begonnen hat;
• - die Dekompression vorschriftsgemäss beendet hat;
• - die Dekompression nicht vorschriftsgemäss beendet;
• - die Anzeigeeinrichtung vor dem Einstieg ins Wasser eingeschaltet hat.

Since every diver often has to carry numerous devices in full gear, it is advantageous if the display device according to the invention also takes over the function of other devices. This makes it easy to replace the conventional depth gauge and diving watch. It also has to take over the function of the altimeter with a resolution of at least 100 m. In addition, the facility should program the following to be able to calculate the ascent conditions, whether the diver:

• - is on land or in water;
• - floats on the water surface;
• - is diving;
• - shows up according to regulations,
• - faster than with l0m / min,
• - shows up too slowly;
• - Dives from previous dives without or with a previous load;
• - exceeds the table to be processed in its values;
• - has exceeded the no decompression limit;
• - must decompress;
• - decompression has started;
• - has finished decompression in accordance with regulations;
• - the decompression has not ended correctly;
• - The indicator has switched on before entering the water.

If an additional time of day clock is implemented in the display device, the readiness of the display device must last - even for several days. Otherwise, a daily clock would not be worth it. In addition, when a time of day clock is taken into account, operation no longer remains when the device is switched off and on, because this clock can also be set and must independently offer the diver the ability to read the time of day.

• 1. Maximale Aufstiegsgeschwindigkeit überschritten ("Ascent-Rate")
• 2. Countdown für die Dekompressionshalte ("Decompression-Countdown", nur dem "Decocompute" unterlagert)
• 3. Power-Down
• 4. Software-Error

7 shows the display field of a practical embodiment of the display device according to the invention. As already described, the display must deliver different displays in different operating states. The most important operating states are "Decocompute" (normal case) and "Out of Range". Further operating states are subordinate to these main operating states:

• 1. Maximum ascent rate exceeded ("Ascent rate")
• 2. Countdown for the decompression stops ("decompression countdown", only subordinate to the "decocompute")
• 3. Power down
• 4. Software error

In a practical version, the display is implemented with four 4-digit LCD numeric displays 13-16 and with three LED indicators 10-12.

Although LCD displays are more advantageous because of their low power consumption and good readability with diffuse and concentrated light, LED display devices should be selected for the most important displays because LCD displays are very difficult or impossible to read at maximum depth and especially in the dark . In order to save electricity on the LED displays, they can be operated clocked if necessary. For example, control via an astable multivibrator with a clock ratio of 1: 1 would theoretically already save 50% of the energy required for this, but under certain circumstances a lower clock ratio of lighting and extinguishing times, e.g. 1: 2 or 1: 3, may be sufficient. If desired, a switch can be provided for this, by means of which the LED displays or only a selection thereof can optionally be switched over from continuous to clocked operation. An adjustable resistor for changing the clock ratio may also be provided in the circuit of the astable multivibrator. The setting handle for this setting resistor is then expediently combined with the handle for the switch mentioned to form a single handle.

• Die Leuchtdiode 10 leuchtet jeweils auf, sobald die maximal zulässige Auftauchgeschwindigkeit von 10m/min überschritten wird.

In the embodiment according to FIG. 7, three LED displays 10, 11, 12 are provided, with which the following is displayed:

• The LED 10 lights up as soon as the maximum permissible ascent speed of 10 m / min is exceeded.

The LED 11 indicates that the counting of the decompression time has started. It lights up as soon as the lowest decompression depth for a particular dive has been reached and goes out when the decompression ends, regardless of whether it has been completed correctly or not. At most, improper behavior of the diver can be indicated by flashing signals from this light-emitting diode 11.

The light-emitting diode 12 indicates when the end of the table of the stored tables is exceeded for some reason or the display device comes out of its normal function for another reason. This LED 12 can then only be extinguished by briefly turning off the main switch 9 on the water surface.

7 shows that in addition to the LED displays 10, 11 and 12, four-digit liquid crystal displays (LCDs) 13 to 16 are also provided. They are used to display numbers and are designed as segment displays.

It has already been stated that the main operating states are designated with the names "Decocompute" and "Out of Range", in the latter case the LED 12 lights up. This indicates that the function of at least the display 16a has been changed with the aid of a switching device, i.e. that the liquid crystal display 16 was connected by switching to another signal transmitter, which possibility was made clear in FIG. 7 by the fact that the left field of the display 16 bears the inscriptions DEDEK and DEMAXD. In this way, an advertisement is saved, which means both a cost and a space advantage.

• - wenn der Taucher die Anzeigeeinrichtung ausserhalb des Wassers (bevor der Taucher sich ins Wasser begibt) eingeschaltet hat;
• - wenn der Taucher nicht eher an die Oberfläche zurückkehrt, als^/er nach den angezeigten Dekompressionsbedingungen zu Ende dekomprimiert hat;
• - solange der Tauchgang die abgespeicherten Tabellen in ihren Maximalwerten nicht überschreitet; und
• - solange die Anzeigeeinrichtung nicht in einen Software-Error läuft.

"Decocompute" means the state of the display device as long as it can and may work according to the stored table values and their processing instructions, ie

• - if the diver has switched on the display device outside the water (before the diver goes into the water);
• - if the diver does not return to the surface sooner than he ^{/ she has} finished decompressing according to the displayed decompression conditions;
• - as long as the dive does not exceed the stored tables in their maximum values; and
• - as long as the display device does not run into a software error.

• - Die Gesamttauchzeit, welche vom Beginn des Abtauchens bis zum Erreichen des Oberflächenbereichs verstreicht, in Minuten: DIVET in Feld 13.
• - Die jeweils aktuelle Tauchtiefe auf halbe Meter genau: DEPTH in Feld 14.
• - Die Auftauchzeit (inkl. der jeweils vorgeschriebenen Dekompressionszeit) in Minuten: UPDIVT (in Feld 15), die der Taucher in jedem Zeitpunkt des Tauchens zu erwarten hat, wenn er mit der maximal zulässigen Auftauchgeschwindigkeit auftaucht.
• -Die jeweils aktuelle Dekompressionstiefenstufe, das ist während des Tauchens die jeweils tiefste Dekompressionstiefe, und während des Dekomprimierens diejenige Tiefe, auf der gerade zu dekomprimieren ist, auf ganze Meter genau: DEDEK in Feld 16a.
• - Die aktuelle Dekompressionszeit in Minuten: DEKOT in Feld 16b. Das ist die jeweils vorgeschriebene Dekompressionszeit auf der Dekompressionstiefenstufe DEDEK.

The following values must be displayed during the "Decocompute" operating state:

• - The total diving time, which elapses from the beginning of the descent until it reaches the surface area, in minutes: DIVET in field 13.
• - The current diving depth to within half a meter: DEPTH in field 14.
• - The ascent time (including the respectively prescribed decompression time) in minutes: UPDIVT (in field 15), which the diver can expect at any time of the dive if he emerges with the maximum permissible ascent rate.
• -The current decompression depth level, which is the deepest decompression depth during diving, and during decompression the depth to which decompression is currently being performed, to the nearest meter: DEDEK in field 16a.
• - The current decompression time in minutes: DEKOT in field 16b. This is the prescribed decompression time at the decompression depth level DEDEK.

These displays can be seen from FIG. 7, the LED 12 simultaneously remaining extinguished and the two LEDs 11 and 10 only lighting up when the corresponding events occur.

In the main operating state "out of range", the converter device 5 (see FIG. 6) is bridged by a shunt (expediently provided within a single integrated circuit), so that the display device now only performs the function of a depth gauge with drag indicator and diving time timer . The "Out of Range" display mode begins as soon as the display device can no longer work according to the stored table values and their processing instructions.

In the "Out of Range" operating state, the decompression times, the decompression depths and the ascent time are no longer determined and the UPDIVT, DEDEK and DEKOT values displayed up to that point are deleted. Instead of DEDEK, field 16 a shows the maximum diving depth previously saved without display: DEMAXD of the dive carried out up to that point.

As mentioned, a switchover device provided and expediently integrated in the display device is used for this purpose. If, for example, the light-emitting diode 11 should have lighted up when this main operating state occurs, it goes out during this operating state, just as the displays 15 and 16b are also deleted. Only the light emitting diode 12 lights up continuously to indicate the changed operating state, whereas the light emitting diode 10 continues to perform its normal function.

In addition to these main operating states, four further operating states were mentioned above. It has already been explained that in the operating state "Ascent rate", i.e.

that is, when the maximum permissible ascent rate is exceeded, the diode 10 lights up and that when the operating state begins, "decompression countdown", i.e. with the start of the counting of the decompression time from reaching the lowest compression level, the diode 1.1. lights up.

The third operating state "power-down" is an operating state in which the display device is to draw attention to a critical value when the battery voltage drops. In practice, this can be done in such a way that the LCD display (s) of the respective main operating state, e.g. every 0.5 seconds, flash as soon as the battery voltage has dropped below a value sufficient for the next two hours. As already explained, the control of the displays via an astable multivibrator saves electricity, which is important in this operating state.

The fourth operating state "software error" means the state in which an error occurs for technical reasons. This assumes that the programs for the display device are created accordingly, i.e. in practical cases, the programs are constructed in such a way that the display device itself can recognize an error in the timing of the programs and thereby switch the display to the software error operating state. From this point on, all functions of the display device are out of operation. All LCD displays are now deleted. Only in the first digit in the display field of the dive time an E appears to indicate the error. The LEDs are all extinguished.

• Zum Arbeiten mit den Tabellen braucht der Rechner die Daten des Tauchganges, im wesentlichen die Tiefe und die Zeit. Die Tiefe wird aus dem Wasserdruck bestimmt, die Zeit wird in einer internen Uhr nachgeführt.

The exemplary embodiment was based on the considerations summarized below:

• To work with the tables, the computer needs the data of the dive, essentially the depth and the time. The depth is determined from the water pressure, the time is tracked in an internal clock.

The diver must be able to see the calculated data and any error messages on a display.

The diver must be able to turn the device on and off and reset the device to its initial state. If clock operation is provided, he must be able to enter the time and possibly be able to switch the display mode to display the time.

When designing the display device to achieve these objectives, it must be taken into account that the device should be battery-operated, ie an operating voltage of approx. 5 - 8 V is available; Any voltage above or with a different sign must be generated from the battery voltage with the corresponding effort; To prevent the battery from discharging too quickly, the circuit must be designed so that it consumes as little power as possible. The battery voltage must be checked and if it drops below a certain minimum this must be indicated; In order to avoid changing the battery in the water and pressure-proof housing, it is advisable to use a rechargeable battery. The device should be installed in a pressure-resistant housing up to 100 m water depth, ie connections to the outside, such as charging connection for the battery, switch axes, etc. represent a great mechanical effort and should be reduced to a minimum.

The heart of the converter device 5 is a microprocessor 27, which i.a. - If it is assigned a program - works as a computer and is therefore usually referred to as computer in the following. For one embodiment of the display device according to the invention, a single chip computer 8748 from Intel is used. This contains lk EPROM and 64 RAM slots (including working register and stack), i.e. Space for 64 variables. If you subtract the stack and the working register (1 bank) from this, there are about 45 variables left for free use. Lk is available for the tables and the program. The ROM and RAM area can be expanded with additional modules.

An estimate of the table sizes shows that 3k additional memory (ROM) is required for the tables.

• - Setzen des Timer/Counter
• - Abfragen des
• - Starten des "
• - Stoppen des "
• - Abfragen eines Timerflags, das einen Timeroverflow anzeigt.

The selected computer has an internal timer / counter that runs in parallel and independently of the program. You need this timer / counter to increase all the time counters in the program and to synchronize the program with the time. The main program can run with the timer / counter in the following ways:

• - Set the timer / counter
• - Query the
• - start the "
• - stopping the "
• - Query a timer flag that shows a timer overflow.

The timer can also intervene directly in the running program via a "timer interrupt" interrupter (with each timer overflow).

Depending on whether a bare counter or a timer is required, the input T 1 or the computer clock (divided by 32 by means of a division stage 23) can be switched to the timer / counter as shown in FIG. 8. To this end, a changeover switch can be symbolically connected to either one of two terminals 18, 19 or a stop terminal 20. The most important commands and their effects can also be seen from the block diagram in FIG. 8.

To start the main program every 0.5 seconds, the timer / counter is switched as an interrupt timer. This means that the crystal frequency must be determined for the computer clock and a timer interrupt program (HTIME) must be written.

6MHz is selected as the quartz frequency. The cycle frequency of the computer is 15 times lower than the quartz frequency, i.e. 400 kHz. The interrupt timer is increased by 1 every 32 machine cycles, i.e. every 80 ps. The interrupt timer is an 8 bit register. By setting this register specifically, times between 80 µs and 256 x 80 ^p s = 20.48 ms can be achieved. These times are too short for the intended application and must be extended by an auxiliary timer program that generates the 0.5 s cycle from 25 timer interrupts. Since the timer interrupt transfers control from somewhere in the main program to the auxiliary timer program approximately every 20 ms, the auxiliary timer program should require as few registers as possible, since these can no longer be used by the main program.

At least one register must be reserved either as an auxiliary timer or as a pointer to the auxiliary timer. A program should be aimed for that only needs one register for the auxiliary timer and for setting the interrupt timer.

In order to obtain the simplest possible auxiliary timer program, the interrupt timer is allowed to run a few times and is initialized with a correction value each time before the jump to the main program (for the first run).

Determine the correction value for the interrupt timer

• - Time interval of the 24 "normal" timer interrupts: 20.4 ms
• - Time for 24 timer interrupts: 24 x 20.48 ms = 491.52 ms
• - Time difference to half a second: 500 - 491.52 = 8.48 ms
• - Required number of timer interrupts: 8.48 ms / 80 ps = 106
• - In order to receive a timer overflow at the desired time, which triggers the interrupt, the interrupt timer must be initialized to 256-106 = 150. The HTIME auxiliary timer program mentioned will be discussed later in the description of the programs. In any case, it can be seen from the above how the timer 7 described with reference to FIG. 6 can be constructed in a practical implementation.

Since the power supply 8 (FIG. 6) can be conventional in terms of its structure, it will not be dealt with in detail and rather the input of the third input value, namely that of the pressure meter 6 and the rest of the circuitry, will be shown in FIGS. 9A and 9B be made clear.

Some requirements for the pressure gauge have already been mentioned above. This must also be resistant to sea and salt water, must provide an electrical output signal for further processing, should also have small dimensions and be cheap.

• - es liefert ein grösseres Ausgangssignal und erfordert daher nur eine einfachere oder gar keine Verstärkerschaltung;
• - es hat dann auch eine geringere Anfälligkeit für Störsignale wie Thermospannungen etc.;
• - Das einkristalline Material mit eindiffundierten Widerständen ist nicht geklebt wie bei den DMS und zeigt damit eine viel kleinere Hysterese (kein Kriechen des Klebstoffes) und keine Ermüdungserscheinungen (solange die Zelle im Nennbereich betrieben wird).
• - Die Herstellung nach den Gesetzen der Halbleiterpysik ist einfacher und ermöglicht Grosserienfertigung zu viel günstigeren Preisen.

The most common systems for electrical pressure measurement are load cells with attached strain gauges (DMS) and piezoresistive transducers. A piezoresistive system was chosen for the display device according to the invention because this has the following advantages over those with strain gauges:

• - It delivers a larger output signal and therefore requires only a simpler or no amplifier circuit;
• - it is also less susceptible to interference signals such as thermal voltages, etc .;
• - The single-crystalline material with diffused resistors is not glued like with the strain gauges and therefore shows a much smaller hysteresis (no creeping of the adhesive) and no signs of fatigue (as long as the cell is operated in the nominal range).
• - Manufacturing according to the laws of semiconductor physics is easier and enables mass production at much cheaper prices.

The selected pressure sensor still has the advantages of a pressure range of 0 to 10 bar and thus a measuring range of up to 90 m water depth and is located in a robust steel housing, whereby the external pressure acts on a steel membrane that is resistant to salt water.

• - durch Umschalten der Verstärkung des Eingangsverstärkers (Differenzverstärkers) 21 gemäss Fig. 9A;
• - durch Umschalten der Referenzspannungsquelle 39 des Analog/Digitalwandlers 22 gemäss Fig. 9A;
• - durch Beschalten eines höher auflösenden Analog/Digitalwandlers und zwar so, dass je nach benötigter Auflösung entweder die oberen oder die unteren 8 Bit auf den Bus geschaltet werden.

The continuous signal of the pressure meter 6, amplified with the aid of an amplifier 21, is expediently to be converted into a computer-compliant, quantized signal, for which purpose an analog / digital converter 22 is provided, which receives the amplified output signal of the pressure meter 6. An analog / digital converter with 8 bit resolution is used because the computer can only process 8 bits in parallel. In order to measure with 8 bit resolution in the zero point, for measuring the height above sea level, with sufficient accuracy, it must be possible to switch over the measuring range. This can be done in the following ways:

• by switching the gain of the input amplifier (differential amplifier) 21 according to FIG. 9A;
• by switching the reference voltage source 39 of the analog / digital converter 22 according to FIG. 9A;
• - by wiring a higher-resolution analog / digital converter in such a way that, depending on the resolution required, either the upper or the lower 8 bits are switched to the bus.

An exact current source would in itself be necessary for the supply of the pressure meter 6 and likewise an exact reference voltage source would be required. However, both stabilized sources can be dispensed with if it is recognized that the pressure gauge practically forms a resistance bridge with the reference voltage source 24, which can be connected directly to the operating voltage in a manner known per se, the reference voltage of the reference voltage source 24 also being applied with a simple resistance voltage divider is the operating voltage, the influences of which cancel each other out, the signal obtained at the output of the analog / digital converter 22 being exactly proportional to that of the pressure meter 6 and thus the water depth.

To save stabilized reference sources, the pressure gauge is connected directly to the 5V operating voltage (instead of 14 V). This reduces the output signal from the pressure sensor. This signal is too small for the analog / digital converter 22 and must therefore be amplified by a factor of approximately 12 so that it is between 0 and 4 V. The amplifier 21 must then be designed in such a way that an operating voltage of only 5 V is sufficient _J and that the amplifier 21 itself can follow a small input signal to zero ("normal" operational amplifiers usually require a supply of + and - 15 V, and the output signal only comes up to approx. 2 V to the supply voltage). A differential amplifier 21 was selected as the amplifier, which will be discussed later.

Of the further parts of the circuit shown in FIGS. 9A and 9B, a comparator stage 41 after the differentiation stage 26 with a purpose to be explained later, and above all the computer 27, which together with a memory stage 28 (EPROM) is the core of the converter device for conversion and Selection of the current or equivalent basic time taking into account the other parameters mentioned. A buffer (latch) for addressing the memory 28 is also connected between the memory 28 and the converter 27.

• - ein Tabellen- und Programmspeicher, beides in der Speicherstufe 28
• - ein Zwischenspeicher (latch) 29
• - der Analog/Digitalwandler 22
• - die Flüssigkristallanzeigen 13 bis 16
• - die Leuchtdiodenanzeigen 10 bis 12
• - falls Tageszeitanzeige erwünscht ist, noch zwei Schalter S3 und S4.

The following are therefore provided as peripheral components of the computer 27:

• - A table and program memory, both in storage level 28
• - A latch 29
• - The analog / digital converter 22
• - The liquid crystal displays 13 to 16
• - The LED displays 10 to 12
• - If daytime display is desired, two switches S3 and S4.

• - einen 8 Bit bidirektionalen Datenbus 42
• - 2 statisch aufzuhaltende (gelatchte) I/O-Ports zu je 8 Bit
• - 2 Testeingänge (wovon, bei entsprechender Programmierung, einer als Eingang für den Zähler (Counter) und der andere als Taktausgang dienen könnte) TO und T1
• - einen Interrupteingang 38

To control these components, the computer 27 has:

• an 8-bit bidirectional data bus 42
• - 2 static latched I / O ports, each 8 bits
• - 2 test inputs (of which, if programmed accordingly, one could serve as an input for the counter and the other as a clock output) TO and T1
• an interrupt input 38

In order to make full use of the computer and to make do with as few additional components (latches, drivers, etc.) as possible, all input and output lines are used as follows:

The data bus is used for data transfer from the memory 28 or from the analog / digital converter 22 to the computer. In order not to control both components at the same time, the correct component must be selected with a control signal (control line: port 2, bit 4).

Port Pl is used to control the display with the following bit assignment:

The binary chip address is converted into the chip enable signals in a 1 out of 4 decoder 36. Since the data is only accepted by the LCD decoder driver with every positive edge of the chip enable signal, this signal must not be applied statically. For this reason, the 1 out of 4 decoder is clocked with the ALE signal. (The ALE signal appears once every computer cycle.)

Port P2 is used for page addressing of the memory for switching from analog / digital converter 22 to memory 28 and for controlling the LEDs (10-12).

Bit allocation:

The LEDs 10-12 are controlled via a jump detection and driver stage 35, which will be described later.

The URL of a value in the external memory 28 is formed from the Pa ^g e-address (Port 2 Bit 0-3) and an address on the data bus. The address part that is transferred on the data bus must be recorded in a latch 29 (CMOS buffer).

Inputs:

A power-down detector (battery voltage threshold switch) TO is used to indicate that the battery will soon be exhausted. Logical "0" at the input TO means that the computer 27 has a flashing display to inform the diver of the limitation of the remaining time. The computer 27 thus also takes on the function of an astable multivibrator.

If a clock is to be implemented, inputs T1 and 28 must be used to set the time of day and to switch the display mode.

The PortPl, as well as bits 5 and 7 of the port P2 of the computer 27 are fed to a display circuit shown schematically in FIG. 9B, which contains the three light-emitting diodes and the four liquid crystal displays, the latter of which is preceded by a decoding and driver stage 30 to 33. The structure of these decoding and driver stages 30 to 33 can be seen in FIG. 10, which will be briefly described below.

The ICM7211 type AM from Intersil was selected as the decoder and driver stage 30-33 (LCD decoder driver). This module contains an oscillator, as well as all the necessary decoding and driver stages to control a 4-digit display. A frequency-determining capacitor is required as an external component. The AM type is microprocessor compatible and has a code that allows a digit to be deleted. It is therefore possible to suppress leading zeros in the display.

• - Die Daten sind ziffernweise mit der entsprechenden Digitadresse zu übergeben. (Die Digitagresse ist ein 2 Bit BCD-Wort)
• - Die Chipselectleitung dient der Chipauswahl, wobei eine Datenübernahme nur auf eine positive Flanke auf dieser Leitung hin erfolgen kann.

10 shows:

• - The data must be transferred digit by digit with the corresponding digit address. (The digital address is a 2 bit BCD word)
• - The chip select line is used for chip selection, whereby data can only be accepted on a positive edge on this line.

• - Zum Auslöschen einer Zahl ist lediglich der binäre Wert 1111 an die entsprechende Digitadresse zu senden.
• - Es besteht bei diesem Code zudem die Möglichkeit, den Buchstaben "E" als Sonderzeichen für eine Fehlermeldung (Error) zu verwenden.

A code which can be seen from FIG. 11 is used for this circuit according to FIG. 10. The following is noteworthy about this code:

• - To delete a number, only the binary value 1111 has to be sent to the corresponding digit address.
• - With this code it is also possible to use the letter "E" as a special character for an error message.

The binary code is shown in column B of FIG. 11 and the hexadecimal code in column HD.

Since the last discussed FIGS. 10 and 11 only serve to explain the very schematic FIG. 9B, a comparison should now be made between the detail 39 of FIG. 9A and two alternative designs according to FIGS. 12 and 13.

When discussing the analog / digital converter 22, it was pointed out above that this only has a resolution of 8 bits. It was also found that the area had to be switched. In this way you can use cheaper components, e.g. with the 8-bit ADC versus a higher bit ADC, finding the end. Range switching can also be advantageous if the pressure meter 6 is not readily able to measure the water and air pressure. In both cases, a single switching device can be used, in which the reference voltage source 24 is switched accordingly.

It has already been pointed out above that for this purpose the amplification of the impedance converter 40 can be switched over in the manner as shown in FIG. 12, and the reference voltage source 24 'is simplified as in FIGS. 9A ( Switching stage 34) and 13, the switches, which are expediently designed as FET switches, are shown as normal switches S for the sake of clarity.

The reason for favoring FET switches is as follows: In order not to use too much energy, the cross current through the voltage divider should be kept as small as possible. That means: the voltage divider should be designed as high-resistance as possible. In order not to burden the voltage divider to the input of the analog / digital converter 22, the voltage divider is connected via an impedance converter ^/ to the analog / digital converter 22nd

• - Alle handelsüblichen FET-Schalter sind mit Speisespannungen von + 15 V und - 15 V zu betreiben;
• - bei einem "gewöhnlichen" FET ist die Abschnürspannung viel zu grossen Streuungen unterworfen, als dass man einen solchen FET mit CMOS-Pegeln ansteuern könnte;
• - der einzige verfügbare CMOS-FET-Schalter (4066) kann wegen seinem On-Widerstand von typ. 3-5k, obwohl er nur eine 5V Speisung benötigt, in obigen Schaltkonfigurationen auch nicht verwendet werden.

Another variant can be seen in FIG. 13, in which the voltage divider (24 ") is switched over in front of the impedance converter (40). The impedance converter 40 can be the same in each case. Both variants (according to FIGS. 12 and 13) are possible, have the following disadvantages:

• - All commercially available FET switches are to be operated with supply voltages of + 15 V and - 15 V;
• - With a "normal" FET, the pinch-off voltage is subject to far too large spreads that one could control such a FET with CMOS levels;
• - The only available CMOS-FET switch (4066) cannot be used in the above switching configurations due to its on-resistance of typically 3-5k, although it only requires a 5V supply.

A switchable reference voltage source 39 was therefore chosen according to FIG. 9A because it is the solution in which the on-resistance of the switch has no influence on the accuracy of the reference switchover, and a CMOS switch can be used. This fact takes into account the fact that the FET switch of the switching stage 34 is located in the input branch of the impedance converter 40, in which practically no current flows, which is why no voltage drop across the on-resistance is to be expected. As can be seen from FIG. 9A, the switching stage 34 contains two switches S1, S2, which are alternately open or closed. On the other hand, an advantage for the alternatives according to FIGS. 12 and 13 could be seen in the fact that only a single switch S is required for the switchover.

The following relationships were found to be particularly useful for the selection of the resistors:

You can set the zero point on the pressure meter 6 with the trim potentiometer R ₄ and the sensitivity of the system via the trim potentiometer R _{1 of} the reference voltage source 24 of the analog / digital converter 22.

As already explained with reference to FIG. 7 and the diode 10, the maximum ascent rate of 10 m / min is to be monitored and an exceedance thereof is to be indicated. This monitoring can be done either digitally or analog. In both cases, the "depth signal." be differentiated.

In order to save space, a software solution would be desirable. In order to get a reasonably realistic display, a pressure change must be made over 2-3 digital steps. be considered, since the last bit can jump for every digital value. Since a depth level actually corresponds to 0.5 m, the diver must travel at a rate of 10 m / min over a distance of 1 - 1.5 m or over a period of 6 - 9 sec. What is required for a cyclical measurement every 0.5 sec to the 12 to 18 variables, the difference of which would have to be continuously formed in order to be able to digitally differentiate the signal. The large number of variables required for this differentiation gives priority to the analog differentiation stage with only 45 variables available at all. The differentiating stage 26 now provided generates a speed signal from the depth signal (travel signal), which must be compared with a signal proportional to the limit value of the ascent rate. The output of this comparison circuit then drives the LED display 10.

• Um die Tauchvorgänge mittels der Eingangswerte Druck und Zeit in ihrer Gesamtheit erfassen zu können, ist das gesamte Programm in die vier aus Fig. 14 ersichtlichen Hauptprogrammteile unterteilt. Jeder dieser Programmteile entspricht auch einem Abschnitt des Tauchganges. Ein Taucher kann innerhalb eines Tauchganges diese Abschnitte in der verschiedensten Reihenfolge durchlaufen; das bedeutet, dass die Programmteile auch entsprechend nacheinander ablaufen müssen.

Programs and operation of the display device:

• In order to be able to record the diving processes in their entirety using the input values pressure and time, the entire program is divided into the four main programs shown in FIG. 14 parts divided. Each of these program parts also corresponds to a section of the dive. A diver can go through these sections in a wide variety of order during a dive; this means that the program parts must also run sequentially.

These program parts will now be explained in connection with the operation of the display device. When the main switch 9 (FIG. 6) is closed, the entire electronics are switched to the operating voltage, the computer 27 (microprocessor) is switched on, setting the program counter to zero, and there jumping to the address of the restart program (RSTART) . The restart program initializes all variables, timers and counters to their initial values. At the end of the restart, the interrupt timer is initialized, enabled and started.

• Der Druck wird im Programmteil PSNORC erfasst und danach die Kontrolle an das Check-and Set-Programm (CHKSET) übergeben. Der Programmteil CHKSET führt alle Timer und Counter entsprechend nach und übergibt die Kontrolle an einen der Programmteile

The main program of the auxiliary timer program (HTIME) is now restarted every 0.5 seconds and then runs as follows:

• The pressure is recorded in the PSNORC program section and then the control is transferred to the check-and-set program (CHKSET). The program part CHKSET tracks all timers and counters accordingly and transfers control to one of the program parts

Surface area (SURFAC) Diving (DIVE) Surface (DIVEUP) Decompression (DECO) Display (DISPLY)

The DISPLY program section operates the display and then changes to a wait loop, which must never finish, since the auxiliary timer must restart the main program beforehand. If the wait loop is nevertheless completed (after approx. 1.5 seconds), the program runs in the software error.

A subroutine collection (LIB) is required so that all programs can work properly. These subroutines are called individually by the various programs.

The description of the individual program parts will be discussed with reference to FIG. 16.

• Da der Rechner 27 nur über ein 8 Bit Indexregister verfügt und der externe Speicher nur indiziert ausgelesen werden kann, muss er (entsprechend dem Indexpointerbereich) in Pages zu 256 Byte aufteilt werden. Die Tabellenspeicherung muss deshalb auch pageweise erfolgen, und zwar für alle 5 Tabellen (für die einzelnen Höhenstufen über Meer) gleich, damit die Tabellen mit den gleichen Programmen gelesen werden können. Bei dieser Abspeicherung entstehen zwangsweise "Löcher" im Speicher, da die Daten ja nicht immer eine volle Page benötigen. Diese Löcherbildung wird durch die unterschiedlichen Tabellenlängen verstärkt. (Die Tabellelänge nimmt mit zunehmender Höhenstufe über Meer ab).

For now, however, some information about the structure of the memories is inserted with reference to FIG.

• Since the computer 27 only has an 8-bit index register and the external memory can only be read out in an indexed manner, it must be divided into pages of 256 bytes (corresponding to the index pointer area). The table must therefore be saved page by page, for all 5 tables (for the individual height levels above sea level) so that the tables can be read with the same programs. With this saving, "holes" inevitably arise in the memory, since the data do not always require a full page. This hole formation is reinforced by the different table lengths. (The length of the table decreases with increasing altitude above sea level).

If you take all of this into account, the 3k table values require approximately 4k memory, which means: one height level requires 3 pages or 3/4 k. So if you use 4k ROM, 1 page (256 bytes) is left for other data or programs.

It has already been mentioned that the computer 27 (FIG. 9A) has an internal lk memory. In view of the large number of data to be processed and the scope of the program required for this, its capacity is by no means sufficient for program storage.

To avoid having to use additional modules, the 4k EPROMs are wired so that they can be used as program and data storage. Since the entire main program, including all subroutines, requires more than 2k of memory, the tables to be saved have a little more than 2k. It can accommodate 3 tables. Because the normal scuba diver generally does not dive at altitudes of more than 2000 m above sea level, only the 3 tables of altitudes 0 - 700 m, 701 - 1500 m, 1501 - 2000 m are saved.

The memory allocation then looks like FIG. 17, the first half of the program in the internal memory 17a of the computer 27 (FIG. 9A), the second half of the program in 17b, the subroutines in 17c and the tables in 17d to 17f Memory 28 are housed. Using pages 7 to 9 in the right part of FIG. 15, e.g. shown that the first half of the decompression table, the second half of the decompression table and the surface interval table, and the page 9 (17i) finally contain the zero time table and the repetitive table. Saving the tables seems tedious, but it is at least cheaper with regard to the components used than if you only wanted to calculate the display values with the help of saving only legal relationships (as far as this is possible at all).

In order to be able to read the tables, a concept for the data structures and the table processing routines must be created. 15 it was shown that the individual tables are accommodated in specific pages in the memory. This is due to the limited addressing options and the requirement that all tables be read with the same subroutines. Now only the arrangement of the individual values in each table has to be defined, in such a way that each value can be accessed as quickly and easily as possible. (Selecting the correct page and table is described later).

Only a linear representation is possible in the table memory, i.e. All tables, whether they are linear (like the zero time table), two-dimensional (like the repetitive group table) or even three-dimensional (like the decompression table), must be brought to a linear form and saved. In order to represent a multidimensional table linearly, position marks (identifiers) for the end of the line, end of the table etc. must be inserted in the table.

To get the smallest possible table, you should try to put several values or one value and one or more identifiers together in one memory location.

• - Mit der maximalen Tiefe und der Bottomzeit sind die Summe der Dekompressionszeiten für einen Tauchgang, die Repetitivgruppe und die Tiefe des 1. Dekompressionshaltes zu bestimmen.
• - Mit der Tiefe, der Bottomzeit und der momentanen Dekompressionstiefe ist die Dekompressionszeit auf dieser Tiefe zu bestimmen.
• - Mit der aktuellen Tiefe ist die dazugehörende Tiefenstufe (gemäss der Dekompressionstabelle) zu bestimmen.

The following routines are required to work with the decompression table:

• - With the maximum depth and bottom time are the sum of the decompression times for a dive, to determine the repetitive group and the depth of the 1st decompression stop.
• - The decompression time at this depth is to be determined with the depth, the bottom time and the current decompression depth.
• - The corresponding depth level (according to the decompression table) is to be determined with the current depth.

With the input values depth and bottom time, a row in the table must be selected each time. The table must therefore be equipped with time and depth level identifiers in such a way that the identifiers can be found easily and compared with the input values.

The data arrangement shown in FIG. 15A was selected in which STID means a depth level identifier, ZID a time level identifier, RG the repetitive group, ZEND a line end mark, STEND a depth level end mark and TABEND a table end mark.

• - Mit einer Ausnahme sind alle Werte kleiner als 64.
• - Alle Tiefenstufen sind mit einer Ausnahme (12m) Vielfache von 5. Der grösste Wert ist 70.
• - Die Bottomtimestufen sind ebenfalls Vielfache von 5, grösster Wert 250.
• - Die Repetitivgruppen gehen von A bis L. Setzt man diese in Zahlen um und setzt auch für den Fall, wo keine Repetitivgruppe vorhanden ist, einen Wert (M) ein, so gehen die Werte von 1 bis 12.
• - Der Wert 0 kommt nie vor.

Now the following is remarkable about the existing tables:

• - With one exception, all values are less than 64.
• - With one exception (12m), all depth levels are multiples of 5. The largest value is 70.
• - The bottom time levels are also multiples of 5, largest value 250.
• - The repetitive groups go from A to L. If you convert these into numbers and also use a value (M) for the case where there is no repetitive group, the values go from 1 to 12.
• - The value 0 never occurs.

• - Man lässt die Zeile, in der die Dekompressionszeit 70 min (einziger Wert grösser als 64) vorkommt, weg.
• - Die Tiefenstufenidentifiers werden durch 5 dividiert abgespeichert. (Ausnahmeregel für die Tiefenstufe 12 m).
• - Die Bottomtimestufenidentifiers werden ebenfalls durch 5 dividiert abgespeichert.

Wird dies konsequent durchgeführt, so sind alle Werte kleiner als 64 und lassen sich in 6 oder 8 Bits darstellen. Das heisst: 2 Bits sind frei für Identifiers und Marken.Taking into account the above findings, the following packaging concept results:

• - The line in which the decompression time is 70 minutes (only value greater than 64) is omitted.
• - The depth level identifiers are stored divided by 5. (Exception rule for the depth level 12 m).
• - The bottom time level identifiers are also stored divided by 5.

If this is done consistently, all values are less than 64 and can be represented in 6 or 8 bits. That means: 2 bits are free for identifiers and brands.

Selected identifiers: ZEND: bit 6 set STEND: bit 7 set TABEND: value 0, since this identifier must be the same in all tables.

The brands ZEND and STEND can thus be saved together with the repetitive group (which is always at the end of the line).

The data arrangement of the decompression table now looks like FIG. 15B.

• Das Auswählen einer Zeile kann mittels "Durchblättern" der Tabelle und Vergleichen des in der Tabelle abgespeicherten Identifier mit den Eingangswerten relativ einfach realisiert werden.

The most important part of the programs for reading the decompression tables:

• The selection of a line can be implemented relatively simply by "leafing through" the table and comparing the identifier stored in the table with the input values.

Readout program (selecting a line in "pseudo Pascal")

• - Die Tiefe des 1. Dekompressionshalts ist der l. Wert in der angewählten Zeile.
• - Die Summe aller Dekompressionszeiten für einen Tauchgang ist die Summe aller Werte zwischen Anfang der angewählten Zeile und der ZEND-Marke.
• - Die Repetitivgruppe steht im gleichen Speicherplatz wie die ZEND-Marke.
• - Aus der aktuellen Dekompressionstiefe kann man die Position einer Dekompressionszeit innerhalb der Zeile und damit deren Wert bestimmen.

Based on this part of the program, the desired values can be easily determined:

• - The depth of the 1st decompression stop is the 1st Value in the selected line.
• - The sum of all decompression times for a dive is the sum of all values between the beginning of the selected line and the ZEND mark.
• - The repetitive group is in the same memory location as the ZEND mark.
• - The position of a decompression time within the line and thus its value can be determined from the current decompression depth.

• BDECOW: Bestimmt folgende Werte: Summe der Dekompressionszeiten eines Tauchganges, Tiefe des 1. Dekompressionshaltes, Dekompressionszeit des l. Dekompressionshaltes.
• BDEKOT: Bestimmt die Dekompressionszeit für eine bestimmte Dekompressionstiefenstufe.
• BRPDEC: Bestimmt die Repetitivgruppe in der Dekompressionstabelle.

The following 3 subroutines were written to read values from the decompression table:

• BDECOW: Determines the following values: sum of the decompression times of a dive, depth of the 1st decompression stop, decompression time of the 1st Decompression stop.
• BDEKOT: Determines the decompression time for a certain decompression depth level.
• BRPDEC: Specifies the repetitive group in the decompression table.

Selecting a line is essentially done in the XDECTB subroutine used in the above subroutines.

The conversion of a current depth to the corresponding depth level is done with a rounding formula in the BDEST subroutine, without using the decompression table, since there are essentially only multiples of 5.

• Zum Arbeiten mit der Repetitivtabelle werden folgende Routinen benötigt:
  • - Mit der Tiefe und der Repetitivgruppe ist der Zeitzuschlag zu bestimmen.
  • - Mit der Tiefe und der Zeit ist die Repetitivgruppe zu bestimmen.
  • - Mit der aktuellen Tiefenstufe ist die nächsttiefere Tiefenstufe (bezüglich Repetitivtabelle) zu bestimmen.

Repetitive tables:

• The following routines are required to work with the repetitive table:
  • - The time allowance is to be determined with the depth and the repetitive group.
  • - The repetitive group is to be determined with the depth and the time.
  • - With the current depth level, the next lower depth level (with reference to the repetitive table) is to be determined.

Therefore, with one input variable - depth - the position of the value in the line can be determined. The second input variable is either the repetitive group, which, when correctly selected, specifies the number of the line in which the time allowance can be found; or the time it takes to compare the value in the table with the row whose position corresponds to the repetitive group.

Taking these findings into account, a data arrangement was chosen that contains no identifiers, but only line end marks. The position of a value in the repetitive group is known if the row and the column in which the value is located are known. The column corresponds to the position of the value within a row. In order to be able to determine this position of the value within a line, the header of the repetitive table (the line with the depth levels) is saved as a pointer line before the actual data, separated by a TABEND mark. The position of the desired value in the line can now be determined by comparing the input value "depth" with the values in the pointer line. It is not necessary to identify the row because the repetitive group has been selected so that it matches the position of the rows in the table.

The selected data arrangement of the repetitive tables can be seen with regard to the pointer line in FIG. 15C and with regard to the table values in FIG. 15D. The data in the repetitive table are saved linearly, starting with the header. The program part for reading the repetitive table, namely determining the position of a value within a line, can be implemented by comparing the depth of the input with the pointer line.

To determine the position within the line, the following results in "pseudo Pascal":

The POS variable now contains the position of the value within the line.

In fact, the variable POS is not "counted up", but determined from the difference of the pointer value at the beginning and at the end of this program part.

• - Den Zeitzuschlag kann man bestimmen, indem man den Pointer um die Anzahl Zeilen vorwärts bewegt.

Based on the program section above, the desired values can be easily determined:

• - The time allowance can be determined by moving the pointer forward by the number of lines.

• - Die Repetitivgruppe lässt sich bestimmen, indem man in jeder Zeile den Wert in der richtigen POS liest, und mit der Eingangszeit vergleicht.

"Pseudo Pascal" program:

• - The repetitive group can be determined by reading the value in the correct POS in each line and comparing it with the arrival time.

"Pseudo Pascal" program:

The next lower depth level can be determined in the pointer line without using the other table values. You simply determine the position in the line and read the next value, but in the pointer line itself.

• BZZU: Bestimmen des Zeitzuschlages
• BRPGUW: Bestimmen der Repetitivgruppe (unter Wasser)
• BDESTN: Bestimmen der nächsttieferen Tiefenstufe

The following subroutines were written to read values from the repetitive table:

• BZZU: Determining the time allowance
• BRPGUW: Determine the repetitive group (under water)
• BDESTN: Determine the next depth level

The position within the line is essentially determined in the subroutine XREPTB, which is used by the 3 subroutines above.

The zero time table is saved and read in the same way as the repetitive table. Thus a pointer line and (in contrast to the repetitive table) only one data line are saved.

For reading out (as with the repetitive table) the position in the line and thus the searched no-stop time are determined first.

On the other hand, if you look at the surface interval table, you can see that the difference from column to column in each row is approximately the same. This is also understandable because a diver always moves from one repetitive group to the next lower after a certain time, and these times should be the same regardless of the starting group.

For this reason, only the lowest diagonal is saved instead of the entire table. Since this table only works with the repetitive groups and only one (diagonal) line is saved, you can save it so that the repetitive group just corresponds to the position in the line.

• Man geht mit der Oberflächenintervallzeit (gemäss der Repetitivgruppe) in die Tabelle und vergleicht sie mit dem dort abgespeicherten Wert. Sobald die beiden Werte gleich sind, wird die Oberflächenintervallzeit auf 0 gesetzt und die Repetitivgruppe um 1 erniedrigt.

Working with this table is very easy under these circumstances:

• You go to the table with the surface interval time (according to the repetitive group) and compare it with the value stored there. As soon as the two values are the same, the surface interval time is set to 0 and the repetitive group is reduced by 1.

So far it has only been described how a particular value is searched within a table. At this point, we will now explain how to find the page in which the table is located in external memory and how to set the pointer to the beginning of the table within this page.

To select the table, depending on the height level, an offset must be determined which corresponds to the page of the first table for this area. Another offset must be added to this offset, which corresponds to the position of the table in the table set. The sum of these two offsets is to be applied as a page address to the bottom 4 bits of port 2. If the page is determined in this way, the table must also be selected, since sometimes 2 tables are accommodated in one page. Therefore, if the table is not at the beginning of the page, you have to "leaf through" the values in the page to the first TABEND mark in order to set the pointer to the beginning of the second table.

To find the beginning of the table, the subroutine FNEXTT was written, which searches a memory area for the TABEND mark and sets the pointer to the value behind this mark.

• Out of Range: Wenn der Taucher in einem (örtlichen oder zeitlichen) Bereich taucht, der mit den Tabellen nicht mehr abgedeckt ist;
• Software-Error: Wenn der Rechner bei einer Rechnung in einen Over- oder Underflow läuft oder der Timer ausfällt.

The previous explanations of the display device itself indicated that it should react to two types of errors, namely:

• Out of Range: If the diver is diving in a (local or temporal) area that is no longer covered by the tables;
• Software error: If the computer runs into an overflow or underflow or the timer fails.

• - Die Grenzen der Tabellen überwacht und bei einem Ueberschreiten dieser Grenzen wird das Out of Range-Flag gesetzt.
• - Bei jeder Multiplikation wird das Resultat überwacht, und wenn es nicht mehr in 8 Bit darstellbar ist, wird das Software-Error-Flag gesetzt.
• - Ebenso würde bei einer Division das Resultat überwacht, bzw. es würde überwacht, ob eine Division durch Null durchgeführt wird. Diese Ueberwachung erübrigt sich aber in unserem Fall, da nie eine Division durch Null vorkommen kann. Der Divisor wird nämlich immer ein Befehl vor dem Aufruf der Divisionsroutine mit einer Konstanten, die immer grösser als Null ist, geladen.

To detect these errors, all table processing routines:

• - The limits of the tables are monitored and the Out of Range flag is set if these limits are exceeded.
• - The result is monitored with each multiplication, and if it can no longer be represented in 8 bits, the software error flag is set.
• - The result of a division would also be monitored, or it would be monitored whether a division by zero is carried out. This monitoring is unnecessary in our case, since division by zero can never occur. The divisor is always loaded a command before the division routine is called with a constant that is always greater than zero.

Now that the storage and handling of the tables has been explained, the program sequence and the program structure will be described. Tables 11 to 18 and 20 to 22 mentioned therein can be found at the end of the description.

Each main program is described in the program documentation and the associated flow diagram. The program documentation is structured in such a way that it describes the flowchart verbally and congruently. Using the flowchart and the program documentation, any desired position in the assembler code can be found quickly and easily.

According to the program structure shown in FIG. 16, the program starts with the restart program RSTART after the main switch 9 is switched on (cf. FIG. 6). This takes place according to Table 11.

The auxiliary timer program HTIME is processed every 0.02 sec according to Table 12, which generates the 0.5 sec cycle with which it cyclically restarts the main program every 0.5 sec, starting with the program part Printer Detection-PSNORC.

In order to be able to record the immersion in water by means of a change in pressure, it must be 0.02 bar in one second. The pressure change of 0.02 bar corresponds to an air column of 200 m. Although no one can get 200 m of air column without jet drive in one second, the diver reaches a pressure change rate of 0.02 bar / s when changing from air to water. A mere 20 cm water column is enough to generate the pressure of 0.02 bar and every diver will dive 20 cm deep within one second when entering the water.

This 20 cm water column results on the one hand from the resolution of the pressure gauge 6 and on the other hand from the fact that the pressure change must be at least 2 digital quanta. If the display device was incorrectly switched on under water (an abnormality), this is recognized by a test that determines whether the first measured pressure is greater than 1.2 bar. This is important because in such a case the air pressure could not be determined in advance.

The reason for choosing the limit of 1.2 bar is that the air pressure at sea level can reach a maximum of 1.06 bar. If you divorce the case that the diver is in a lake dives, the height of which is below that of the sea level, the test to 1.2 bar can easily be made.

If the main switch 9 is actually only operated under water, the display device operates on the assumption that the air pressure at the dive site = 1 bar. From this point in time, the depth gauge of the device according to the invention is only as good as most conventional depth gauges, which do not differentiate between diving in mountain lakes and the sea.

1 bar corresponds to the air pressure at sea level and is therefore the zero point for our system from which either the water depth or the height above sea level is determined.

The program sequence of the program part PSNORC can be seen in detail from FIG. 17 and from Table 13.

43 mean a test as to whether the display device was switched on under water; 44 a test of whether the diver has entered the water; and 45 a conversion of the pressure so that it is adjusted to the gain = 1.

At this point it should be added that 10 bar in the computer 27 or in the analog / digital converter 22 each correspond to 200 bits, so that one bit gives a resolution of 0.5 m. This means that the depth gauge is accurate to 0.5 m, which makes it very easy to prepare the data for use in the tables, since the digitally determined depth divided by two corresponds exactly to the real depth in meters. However, the ratio of 10: 200 means that the numerical value of the pressure processed in the computer is too large by a factor of 20 compared to the actual pressure. It should also be mentioned that the calculation of the diving depth by means of the pressures PNEU and PNULL is reduced to:

DEPTH: = (PNEU-PNULL)

This means that the dive depth maintained in the computer is 2 times greater than the actual dive depth.

16 further shows that the program part PSNORC is followed by the program CHKSET, the details of which can be found in table 14.

The library program shown in FIG. 16 should also be discussed at this point.

• - Alle oben beschriebenen Tabellenabarbeitungsroutinen.
• - Einige mathematische Programme.

All subroutines used are housed in this part of the program. These are:

• - All table processing routines described above.
• - Some math programs.

• - Eine Subtraktion mit direktem Zugriff zum Minuenden.
• - Eine Subtraktion mit indirektem Zugriff zum Minuenden. (Beide Subtraktionen übergeben im Carry-Bit die Vorzeicheninformation und sind so auch für den Vergleich zweier Zahlen verwendbar.)
• - Eine Multiplikation mit direktem Zugriff zum Multiplier. (Diese Multiplikation von 8 x 8 Bit liefert ein 16-Bit-Resultat. Das 16-Bit-Resultat aus Lower-8-Bit und Upper-8-Bit wird lediglich im Hauptprogramm DISPLY verwendet, sonst wird nur mit den Lower-8-Bit gerechnet.)
• - Eine Division mit direktem Zugriff zum Divisor. (Die Ursprüngliche 16-Bit durch 8-Bit Division wurde in eine 8-Bit durch 8-Bit Division abgeändert, da der Rechner mit 8-Bit Werten arbeitet. Um einen Fehler zu testen, kann das Carry-Bit herangezogen werden, welches im Falle eines Overflows gesetzt ist.)

In this sense, the library program has:

• - A subtraction with direct access to the minute end.
• - A subtraction with indirect access to the end of the minute. (Both subtractions transfer the sign information in the carry bit and can therefore also be used to compare two numbers.)
• - A multiplication with direct access to the multiplier. (This multiplication of 8 x 8 bits provides a 16-bit result. The 16-bit result from lower-8-bit and upper-8-bit is only used in the main program DISPLY, otherwise only with the lower-8- Bit calculated.)
• - A division with direct access to the divisor. (The original 16-bit by 8-bit division was changed to an 8-bit by 8-bit division because the computer works with 8-bit values. To test an error, the carry bit, which is in the If an overflow is set.)

A subroutine that converts 8-bit and 16-bit binary numbers into BCD numbers in order to be able to send the values to be displayed to the display in the BCD code. In addition, this subroutine recognizes leading zeros and sets the (F) -Hex instead of the leading BCD zero, thus the code required in FIG. 11 is taken into account for the blank. It would be an advantage if the library was not saved as a coherent program block, but rather that the individual subroutines were inserted into the main program in such a way that as many pages as possible were used, ie that there were few "holes" in the program memory and few page jumps were necessary will. Nevertheless, this is not recommended for the program structure described, because the entire program requires approximately 2 1/4 K memory, ie memory bank switching must be used. For the sake of simplicity, we put all subroutines behind the 2 K limit, so that the memory bank only has to be switched before and after each call "subroutine" and the main program never goes beyond the 2 K limit, which is to be avoided as much as possible, because that way memory bank switching would be much more complicated.

In the CHKSET program part, depending on the values or value differences determined in the context of this program, the decision is made as to which of the programs that follow the CHKSET program part in FIG. 16 must be processed.

The sequence of the SURFAC program part can be seen in FIG. 18 and in table 15. Details of the Diving program section, DIVE, are shown in Table 16.

46 means a test whether the diver is snorkeling; 47 a test of whether the diver is leaving the water; 48 a test of whether the diver has switched to diving; 49 a test of whether the diver is in a surface interval; and 50 a test of whether the repetitive group has become zero.

Surfacing program, DIVEUP: In order to be able to control the surfacing at a minimum speed of 8m / min, the diver must be "observed" over a longer period of time. This "observation" consists in checking whether the diver is in the "ascending cone". The surfacing cone is the area that the diver travels over a period of 30 seconds, surfacing at least 4 m in the direction of the vertical and not diving below the depth level at which the surfacing started. A new ascending cone is set every 30 seconds if the diver has not left the ascending cone and continues to emerge. The sequence of this program is shown in table 17.

The Decompress, DECO program is described in more detail in Table 18.

All of these programs, as can be seen particularly from FIG. 7, lead to some type of display to which the program display, DISPLY is assigned.

In order to be able to control the four displays 13 to 16 (cf. FIGS. 7, 9B) with four-digit numerical displays, a total of 16 digits must be addressed. These 16 digits are addressed by a four-digit (4-bit) code word, which has the structure shown in Table 19. The code word for the selection of digit No. 3 in display 15 is ^: ( ^B ) _H ex

This structure of the code word makes it very easy to send the individual display values to the display. You can now count up a display counter (D-ISPCO) from zero to 15 and send out the relevant digit in the BCD code to the display each time. Table 20 illustrates the flow diagram of this program part.

Now that the individual program parts have been described, reference should also be made to Table 21, in which all program parts are shown in a memory allocation plan for program storage. Table 22 contains a list of all the variables and subroutines used.

The status and flag conventions are also shown in the following tables 23 and 24.

It should be noted that it emerged from the above explanations that essentially the tables of the pressure chamber laboratory of the University of Zurich were stored in the table memories, because they are particularly suitable for assembling the entire dive from individual dive sections, the possibility of evaluating previous dives in one Have a repetitive dive and not only refer to dives at sea level, but also in mountain lakes up to 3200 m. Above all, digitization is easy to carry out. However, it is to be understood that the invention is in no way limited to the use of these tables, but that other tables, such as e.g. those of the U.S. Navy may apply.

Although no particular display for the respective time of day was shown and described with reference to FIG. 7, it was mentioned in the description that the use of the timepiece, which is present per se, is advantageous for specifying the time of day. This means that even after the main switch 9 is switched off, the power supply to the circuit parts to be assigned to this time display is maintained.

Decompression table for 0 - 700 m above sea level

Repetitive system for 0 - 700 m above sea level

Surface interval table (min)

Decompression table for 701 - 1500 m above sea level

Repetitive system for 701 - 1500 m above sea level

Claims (16)

l. Display device for the parameters of a dive, such as current depth, maximum depth immersed, previous dive time or the like, which display device is used a) at least one memory for the decompression parameters for a series of diving depths and times, and b) an evaluation and linkage stage for the measured values of the depth gauge and the timepiece is controlled with the values stored in the memory,
characterized in that the total ascent time required, depending on the depths and times immersed, including the prescribed decompression stops, can be displayed at every point in time of the dive and / or a converter device (5) for the current basic time when entering a new depth level in this new depth level equivalent basic time is provided. 2. Device according to claim 1, characterized in that with the aid of the converter device (5) the air pressure, preferably measured with the aid of a measuring device (6), can also be taken into account. 3. Device according to claim 2, characterized in that a single, preferably having a piezoresistive measuring cell, pressure gauge (6) for both the air and water pressure is connected to the circuit containing the transducer device (5). 4. Device according to claim 3, characterized in that the measuring range of the pressure meter (6) can be switched over for air or water pressure measurement with the aid of a switching device (34). 5. Device according to one of claims 1 to 4, characterized in that a differentiating stage (26) is connected to the output of the pressure meter (6). 6. Device according to claim 4 or 5, characterized in that the switching device (34) comprises a jump detection stage (35) for the pressure, which is formed, for example, by the differentiation stage (26). 7. Device according to claim 4, 5 or 6, characterized in that - e.g. for an evaluation and logic stage limited working area - with the help of the switching device (34) by switching the gain or the bit range of an upstream of the analysis and logic stage analog-digital converter (22) a range switch can be carried out. 8. Device according to claim 7, characterized in that a switchable by the switching device (34) reference voltage source (24, 24 ', 24 ") is provided, which is advantageously followed by an analog-digital converter (22). 9. Device according to one of claims 4 to 8, characterized in that the switching device (34) has at least one FET switch. 10. The device according to claim 9, characterized in that an impedance converter (40) is connected downstream of the FET switch for decoupling from the input of the downstream stage, in particular of the analog-digital converter (22). 11. Device according to one of claims 1 to 10, characterized in that when an abnormal function occurs by a detector circuit consisting of a timer and a pressure sensor (6), a warning signal (12) and / or a drag value display (16a) for the maximum diving depth reached can be switched on. 12. Device according to one of claims 1 to 11, characterized in that the converter device (5) has a computer (27) and memory for base times and / or decompression times and / or repetitive groups. 13. Device according to claim 12, characterized in that the memory (s) is (are) a table memory (28). 14. Device according to one of claims 1 to 13, characterized in that the converter device (5) has a memory circuit for the depths and times immersed in each case, and optionally for the resulting correction values. 15. Device according to one of claims 1 to 14, with at least one segment display, characterized in that the segment display (16a) alternately - e.g. before and after the occurrence of an abnormal function - can be switched to display various information. 16. Device according to one of the preceding claims, characterized in that an astable multivibrator circuit for clocked activation of at least one display (10-12) is provided.

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