EP0550649B2 - Device for monitoring portable breathing apparatus - Google Patents

Abstract

A monitoring device for portable breathing apparatus has a manometer that detects the pressure in the pressure reservoir (5) of the breathing apparatus and an emitter (2) that emits at regular intervals a signal that corresponds to the pressure. The emitter further has a signal generator that generates an identification signal charactheristic for the emitter. The pressure signal and the identification signal are received and checked by a receiver (3). When the identification signal matches an identification comparison signal stored in the receiver, the pressure measurement value is displayed on a display (4).

Description

The present invention relates to a monitoring device for mobile breathing devices. Mobile respirators of this type e.g. by divers, by firefighters at the Firefighting or generally used when the Air is contaminated with pollutants that allow free breathing to make impossible. Mobile breathing devices usually exist one or two metal bottles, e.g. on the back carried by the user and in which a highly compressed oxygen-gas mixture with a pressure of e.g. up to 350 bar is included. This oxygen-gas mixture is simplified in the following as breathing air or simply called air. The air we breathe becomes the bottles removed via a shut-off valve and by the user of a so-called lung regulator.

The problem of using such breathing equipment will be First described using the example of scuba diving:

When scuba diving today, in professional Use, depths of over a hundred meters reached, and also When scuba diving, experienced divers become considerable Lows achieved.

As the water depth increases, that on the diver increases acting hydrostatic pressure, which causes the Body tissues a higher amount of inert gases, i.e. in particular absorbs nitrogen. When surfacing and the the associated reduction in pressure reverses Operation around. Does the pressure decrease faster than the released gas can be removed and exhaled, the decompression sickness arises, which in lighter ones Cases of temporary health impairment, in more severe cases but permanent damage to health and can even lead to death. To release too quickly To prevent the inert gases, divers must Reappear after a longer stay in larger Take longer pauses in depth at certain depths, which are referred to as so-called decompression stops. The duration of the necessary decompression stops is difficult to calculate because the human body has a Has a variety of different types of tissue both in terms of saturation and desaturation behavior depending on diving depth and Dive time as well as in the medical hazard differentiate. Therefore, divers usually use Diving tables in which the decompression times in Dependency on the depth reached and the Dive time is specified, or they use dive computers, in which the saturation and desaturation behavior of a selected number of tissue types mathematically simulated and the decompression times thus determined for the diver be displayed via appropriate display devices.

An overview of the problem of decompression gives e.g. the work of A.A. Bühlmann: Decompression-Decompression Sickness, Berlin, Heidelberg, New York, Tokyo 1984, ISBN 3-540-13308-9, in particular pages 1 - 62 from the medical aspect, and pages 63 - 67 about the Decompression calculation. Pages 68-82 contain Decompression boards for divers.

So before the diver undertakes such a dive, he must ensure that the person he is carrying Air supply for the planned length of stay and for the Ascent time is sufficient.

However, the determination of the required air supply comes up short on significant difficulties: that of the diver per minute Air intake is not constant, but changes e.g. with the physical strain. With fear and Air consumption can be caused by panic conditions so-called hyper ventilation increase by leaps and bounds. Farther the amount of air withdrawn is of course from depends on the respective ambient pressure and therefore depends on it which depths the diver seeks.

The diver therefore needs a monitoring device the actual air consumption and the still possible To be able to estimate the length of stay under water.

Currently divers use it to monitor the air supply Pressure gauges that are connected to the breathing apparatus by a hose are connected and the current pressure of the air supply in the Show container. As the pressure increases with the removal the air from the bottle sinks can, accordingly Experience provided, to some extent, the remaining one Breathing time can be estimated.

It has also been suggested, see e.g. U.S. patents 4,794,803 or 4,586,136, a monitoring device in such a way that from the measured Bottle pressure immediately increases for the diver Remaining time can be determined and displayed can. However, these devices have the disadvantage that connecting them to the breathing apparatus via a hose and are therefore very unwieldy to use and also may affect the diver's range of motion.

To counter this problem is in the Australian Patent document AU-B-78218/87, to form the preamble of claim 1 and of claim 33 was used, been proposed instead the hose an ultrasound transmission between the Pressure sensor on the bottle and a display device to provide. The reception and display device is in in this case arranged on the face mask of the diver.

The use of such monitoring devices especially when using wireless signal transmission work, but is only responsible if certain Security requirements are met.

So it must be ensured that the signal transmission from Sender to receiver done correctly under all circumstances, i.e., movements of the diver and water, external Interferences etc. have no influence on the transmission of the Have measurement signal.

It should be borne in mind that from one Depth of about 30 m due to the high N2 partial pressure, the has a kind of narcotic effect (deep intoxication), is impaired. If the monitoring device e.g. incorrectly indicates that the air supply is too low, this can lead to thoughtless, even with experienced divers cause panic-like reactions. So it should be sure that the monitoring device As far as possible, not even briefly, a wrong signal displays.

The problems described above for scuba diving meet, in a correspondingly modified manner, also for the Use of breathing apparatus for fire and disaster control and in other applications too. Here too the user needs an exact specification of the Available breathing time, e.g. his way back to be able to start accordingly in time. Farther here, too, the user is usually in one particular state of stress, and care must be taken that incorrect measurements and incorrect information are avoided as far as possible become.

The present invention is therefore based on the object a device for monitoring mobile breathing apparatus create through which the user at least over his Air supply is informed and the reliable and works in particular free of external interference and whose display is easy to read. It is further object of the invention, a corresponding method to monitor mobile respirators.

This object is achieved by the subject of Claim 1 solved.

The inventive method is the subject of the claim 33.

Preferred developments of the device are Subject of the subclaims.

The monitoring device according to the invention consists of a transmitter and from a separate from this Receiving device. This design has the advantage that the receiving device, which is usually immediately with the display device is combined, in the field of vision of the User can be arranged without it Freedom of movement, e.g. through a hose device, is unnecessarily restricted and without having to read the Display device requires special handling is.

The receiving device can thus in any way from Users are worn. It is preferable that the Receiver directly on the wrist of the User is arranged. Opposite an arrangement on a Face mask, this has the advantage that the user does not Accommodation difficulties when reading the display Has. In addition, he does not always have that Display instruments in view, what irritate him or could distract. The arrangement on the wrist allows that User, the corresponding displayed data even then easy to read if it e.g. any work with your hands.

On the other hand, wireless signal transmission harbors considerable Risks to the security of data transmission. The receiving device could with this conception Interference signals, e.g. through movements of the diver, but also caused by external sources as Interpret the pressure signal and thus incorrect, or show changing values more often. The user it is then no longer possible to make the data reliable read.

A risk that should not be underestimated goes to the wireless transmission also assume that appropriate Usually missions or dives alone be undertaken, but that several people take the Use or do the dive together. There within a rescue organization or diving center often identical for all members of such a group Devices are used, the risk is very high that a Receiving device the signals of the transmitting device Neighbors and thus the user wrong values displays.

It is possible to solve the problem of using multiple Solve monitoring devices within a group by that each device is assigned an individual transmission frequency that is only set by a corresponding Receiving device can be received. This design has but some drawbacks. If you wanted a larger number such monitoring devices with different To make frequencies available would have to be for that individual device remaining frequency band very narrow his. However, this requires a relative one on the receiver side high technical effort to get out of several received frequencies reliably those for the respective Filter out the receiving device specific frequency. Thereby the receiving device becomes complex, and the probability possible error increases.

Even the fact that the intensity of the received Signals decreasing with distance is not enough to in this case a clear assignment of the devices ensure.

For one thing, it would be reasonably constant Reception intensity can only be achieved when the transmitter and receiver in a relatively short distance are arranged to each other and always the same spatial Have assignment to each other. But this is already then not the case when the transmitter on the pressure vessel and the Receiver in the area of the head or e.g. a face mask installed by the user. In this case it is enough already a turn of the head to the spatial assignment and thus to change the reception intensity. Is the Transmitter on the pressure vessel and the receiver on the wrist of the Installed depending on the user User movement, with large fluctuations in the Reception intensity to be expected. In addition, more Disturbances, e.g. Air bubbles when diving, the reception intensity additionally influence.

Furthermore, the distance from different users, e.g. when collecting objects together or people, be very small, so the distance-related Difference in intensity no longer matters. This applies e.g. then when a diver tries to to help colleagues in difficulty.

The monitoring device according to the invention solves this Problems very reliable. By using a Identification signal ensures that each Receiving device only receives and processes the signals, broadcast by the assigned transmitter become. This not only prevents signals other devices can be received; because of the rigid predetermined identification pattern is also prevented that signals are processed by external Disturbances, e.g. from any other channels. This is achieved in that the signal is only processed further if it exactly matches the respective identification pattern corresponds. That interference signals from others any transmitter corresponding identification pattern included is very unlikely.

According to a preferred embodiment, this happens Transmission of the data and the identification signal digital. This will increase the reliability of the Data transfer is achieved and it is also possible to choose a high number of identification patterns by this signal from a correspondingly high number of individual Bits is put together.

It is possible that each part of the broadcast already at the Production of a specific receiving part or vice versa is assigned. However, this has the disadvantage that e.g. in the event of a failure of the receiving part, the associated one Transmitting part also becomes unusable and vice versa.

According to a preferred development of the invention therefore proposed the assignment between the transmitting part and To make the receiving part changeable.

In this case, it is preferably provided that the Transmitting part and the receiving part to be used with it brought into an identification signal change mode can be, which enables the receiving part, the Identification signal of the transmitter part assigned to it record and save. This assignment or According to a preferred development, the pairing mode has multiple security levels so that an unintended and incorrect assignment of transmitting part and receiving part is avoided.

According to a preferred further training, transmission and Receiving part designed so that the identification signal change mode always from one device, and preferably from Transmitting part, is triggered, this device then preferably also a fixed, unchangeable identification signal owns.

The possibility of free assignment of the transmitting part and Receiving part has considerable in practical use Benefits. Organizations such as a dive center, a Fire brigade units and the like usually have one Variety of mobile breathing devices that use the monitoring device according to the invention each with a Transmitting part and a receiving part are provided. Falls in such a group e.g. a transmitting part and a receiving part of an unassigned pair, would unchangeable assignment a total of two monitoring devices become unusable. Using the remaining assignment could be changed Devices continue to be used.

After all, it is also not necessary to receive part and transmit part so that a Confusion of devices is impossible. It is found that the devices do not fit together can at any time new assignment can be made.

Furthermore, especially if the monitoring device should be used when diving, both when Transmitting part as well as necessary battery at the receiving part be arranged pressure-tight in the respective housing and cannot be changed by the user himself. There it is to be expected that the batteries of the transmitter and Receiving part, depending on the respective usage profile, would be consumed at different speeds for the Time of battery replacement of a device, which is usually can only be made by the manufacturer, both devices such a combination fail. This disadvantage too is avoided by the changeable assignment.

The variable assignment also has the advantage that one Sending device can also be assigned to two receiving devices can. It is then e.g. possible that a diving instructor has two Receiving devices used with which he kept his air supply and the air supply of a student diving with him can watch. If the devices also have a Air consumption measurement are provided, the instructor can moreover from this display the stress state of his Judge the student.

Finally, it is also conceivable that, in particular for the Receiving device that combines with other functions different device models can be offered that the user should be able to use without having to to have to procure a new transmission part each.

Furthermore, the manufacture of the monitoring device significantly simplified by the changeable assignment.

The identification signal change mode is preferred triggered by the transmitter by a manual Activity is caused to give a particular signal that Identification control signal to be sent out to the Receiving device indicates that an assignment process to be held. To assign multiple receivers to prevent a sending device, on the part appropriate safety measures on the receiving device be provided.

The actual assignment is done by using the Identification control signal also the identification signal of the transmitting part is broadcast. That in the identification signal change mode brought receiver receives this identification signal and stores it in a corresponding memory until it is in the frame a new assignment another identification signal receives.

It is unlikely that a third, arbitrary Transmitter emits a pattern that is the identification signal corresponds. The remaining small uncertainty factor can be greatly reduced by another security measure which also serves to reduce the effects of signal interference, such as by movements of the diver are caused to eliminate.

One of the preferred goals of the monitoring device is the calculation of the user of the breathing apparatus Available breathing time. This breathing time is preferred calculated by a computing device that either is installed in the sending device or in the receiving device. This allows the user to see the breathing apparatus how long the air we breathe at the current Conditions will still suffice.

According to a preferred development of the invention this computing device is installed in the receiving section and performs the air consumption calculation in the sense of a forecast if no signal is received from the transmitter. Thereby can receive a signal after an interruption its plausibility will be checked.

So if the receiving device due to a fault receives no signal, it calculates the air consumption so long due to the previous measurements continue to be high until the next signal is reliably received. Then it will be checks whether this received signal in a certain Tolerance range of the projected air consumption is. If so, the signal is considered a new value displayed. If this is not the case, there is no display. Also preferred is as long as the reception situation is unclear, no display value is output.

This design has the advantage of being reliable can be prevented that the receiving device due to an incorrectly received signal displays an incorrect value that could irritate the user.

The transmission of the signals from the transmitting part to the receiving part can with all suitable for the signal transmission Procedure. If the monitoring device is under Water is used, the data transmission can be done with Ultrasound done. One is particularly preferred Use under water, however, the use of radio signals, and here in particular the use of signals in the long wave range, i.e. the use of radio signals with a frequency of 5 Hertz to 100 Kilohertz.

Investigations by the inventors have shown that for electromagnetic transmission of the signal in the water Frequency range between 5 Hertz and 50 Kilohertz especially is suitable to transmit the desired signals.

Both the transmitter and the receiver can be used other functions.

If the monitoring device is used when diving, can, according to a preferred training of the Invention, combined with a decompression calculator become. This computer is preferably in the receiving section housed and is connected to a pressure sensor, the the hydrostatic pressure of the water and thus the Measures depth. It is also another timer provided by which the diving time is measured can. By means of a computer circuit, the measured Values of diving depth and diving time the saturation or Desaturation behavior for a finite number of Tissue types determines how this e.g. in the quoted work by Buehlmann is shown. Can be determined from these values and showing the diver how long the ascent is to the water surface as a whole, and in which Deep decompression stops with which length are to be inserted. By combining the calculation of the Decompression times with the air consumption calculation can then calculated and shown to the diver how long he is still at the appropriate depth level can stop before he has to start to climb enough air supply for a medically safe To have ascent available.

It is known from diving medical research that the Saturation and desaturation not only of tissues Depth and time depends, but also on it depends on whether the diver is a physiological Provides work performance or not. Does the diver work during the dive, so the required decompression times by up to 50 percent increase. A corresponding increase in decompression times can also result if the diver, e.g. at the Scuba diving, while not actually doing any work, but e.g. its location against a stronger current must hold, so that also a higher physiological Work performance is required.

According to a preferred development of the present Invention is the physiological work performance with the help the monitoring device according to the invention in the Decompression calculation included. As a benchmark for Air consumption measurement is used. The air consumption measurement can both be done relatively as well as absolutely.

With an absolute air consumption measurement, the Decrease in pressure with known bottle volume determined, what amount of air the diver takes in per unit of time. Of this value is based on an average or a increased physiological work performance that closed is then taken into account in the decompression calculation.

With the relative air consumption measurement only determined how high the average air consumption of the Divers is what is averaged over a period of time becomes. If the air consumption increases compared to this value, is characterized by increased physiological work output went out.

Both the absolute and the relative air consumption measurement can be continued while surfacing to to influence the decompression calculation further. Thereby it is possible to perform a physiological work during the decompression phase, which in the Usually the decompression time is shortened. In addition to Air consumption measurement can also be done using an appropriate Sensor detects the pulse rate of the diver and to the Decompression meter can be transmitted. The pulse rate also provides a measure of the physiological Work performance. If the pulse frequency is e.g. over electrodes removed, which is arranged in the chest area of the diver the values can e.g. by means of a cable connection forwarded to the transmitter on the scuba tank and thence wirelessly with the monitoring device to the Wrist-worn receiving device can be transmitted.

When using the monitoring device in the fire and Combating disasters can also do several additional functions can be integrated in the receiver. In addition to displaying the current pressure in the Pressure vessel of the breathing apparatus the remaining one Breathing time and / or breathing rate calculated and displayed become. It is also possible in the receiving device Provide measuring sensors that provide the user with information about give the condition of the surrounding air. For example, at fire fighting the carbon monoxide content in the air measured and displayed so that the user of the Breathing apparatus e.g. about the danger of those to be saved People is informed. Of course, except Gas detectors but also sensors for all other types of measurable damage (e.g. Geiger counter and the like).

Fig.1:

Eine schematisierte Funktions-Darstellung eines mobilen Atemgerätes mit einem Ausführungsbeispiel der erfindungsgemäßen Überwachungseinrichtung;

Fig.2:

eine schematisierte Darstellung des Sendeteils des Ausführungsbeispiels gemäß Fig. 1;

Fig.3:

eine schematische Darstellung der Funktionsmodi des Sendeteils des Ausführungsbeispiels gemäß Fig. 1;

Fig.4:

eine schematische Darstellung der Codierung des Sendesignals des Ausführungsbeispiels gemäß Fig. 1;

Fig.5:

eine schematisierte Darstellung des Aufbaus des Sendesignals im Normalbetrieb des Ausführungsbeispiels gemäß Fig. 1;

Fig.6:

eine schematisierte Darstellung des Aufbaus des Sendesignals im Identifikationsänderungs-Modus des Ausführungsbeispiels gemäß Fig. 1;

Fig.7:

eine schematisierte Darstellung des Empfangsteils des Ausführungsbeispiels gemäß Fig. 1;

Fig.8:

eine schematisierte Darstellung eines weiteren Ausführungsbeispiels der Erfindung, bei der die Empfangseinrichtung mit einem Dekompressionsrechner kombiniert ist.

An embodiment of the present invention will now be described with reference to the figures. In it show:

Fig.1:

A schematic functional representation of a mobile breathing apparatus with an embodiment of the monitoring device according to the invention;

Fig. 2:

a schematic representation of the transmitting part of the embodiment of FIG. 1;

Fig. 3:

is a schematic representation of the functional modes of the transmission part of the embodiment of FIG. 1;

Fig. 4:

a schematic representation of the coding of the transmission signal of the embodiment of FIG. 1;

Fig. 5:

a schematic representation of the structure of the transmission signal in normal operation of the embodiment of FIG. 1;

Fig. 6:

a schematic representation of the structure of the transmission signal in the identification change mode of the embodiment of FIG. 1;

Fig. 7:

a schematic representation of the receiving part of the embodiment of FIG. 1;

Fig. 8:

is a schematic representation of another embodiment of the invention, in which the receiving device is combined with a decompression computer.

The first explained with reference to FIGS. 1 to 7 Embodiment of the invention is intended in Used with a diver's breathing apparatus become. However, it can also be done with appropriate Modifications also for breathing devices, such as e.g. at the Fire and disaster control are used Find.

Fig. 1 shows a highly schematic representation of the Monitoring device, generally designated 1 and is a transmitting part 2, which is the transmitting device includes, and a receiving part 3, the receiving device includes, has.

The transmitting part 2 is, in the present example, (in the Fig. Not shown) firmly on a diving bottle 5th appropriate. The diving bottle is a conventional one Steel bottle with a volume of e.g. 7 to 18 liters and a maximum storage pressure of e.g. 350 bar, which can be closed with a manually operated shut-off valve 6. The shut-off valve 6 is open during use, and the pressure of the air supplied to the user is above a schematically indicated pressure control valve 9 regulated. This valve 9, which is usually used as a regulator is one of the different types have, which are known in the prior art. The The user then removes the air from the breathing apparatus, e.g. about a (not shown) hose connection by means of a Mouthpiece.

There is a between the shut-off valve and the regulator Pressure sensor 7 arranged in the bottle prevailing pressure. The arrangement of the pressure sensor after the shut-off valve 6 has the advantage that the Pressure sensor during storage of the bottle with the Device pressure is applied; still has this as before is explained, advantages in terms of security design the monitoring device.

The receiving part 3 is in use in spatial Distance to the transmitting part 2 used and is with a Coupled display device 4, which is usually directly integrated into the housing of the receiver is.

The transmitting part 2 shown schematically in FIG. 2 has one of non-magnetic material, preferably Plastic, existing housing 10 in which the electrical and electronic components of the transmitting part are included. The inside of the housing 10 of the transmitter part 2 is completely with electrically non-conductive oil, Filled silicone or the like. The area of the housing 10a, in which the pressure sensor 7 is arranged, is so designed that the pressure in the bottle 5 is exposed. This is due to the connecting piece 11, 12 shown schematically. The remaining part 10b of the housing is also sealed to prevent water ingress avoid.

A battery 13 is also accommodated in the housing 10, which supplies the transmitter with electrical energy, and which is therefore also exposed to the pressure in the housing.

The structure of the electrical components of the transmitting part is now described with reference to FIG. 2.

The pressure sensor 7 is via electrical lines here and are only shown schematically below, connected to a signal conditioning circuit 20. As Pressure sensor can be all commercially available sensor types can be used, provided that they are used with a Battery voltage of less than 5 V can be operated and use as little energy as possible. Especially to Therefore, pressure sensors based on the piezoelectric are preferred Working principle.

The analog signal from the pressure sensor is in the signal conditioning circuit 20 into one using an A / D converter digital signal converted. The signal conditioning circuit 20 is still with a quartz controlled timer 21 connected, the purpose of which will be explained below. The digitally processed signal becomes a commercially available one Microprocessor computing unit 22 supplied. The microprocessor computing unit 22 is connected to a memory 23 and also receives the signals from the timer 21. The Memory 23 (and the corresponding memory in the receiving section) can be built entirely from RAM memory elements his. But it is also possible to use a mixed storage, consisting of ROM (read-only memory) and RAM memory elements to use. Since the battery voltage is permanently Is available, the memory contents can also be found at Long-term use of volatile memory elements be secured.

By the microprocessor 22, the pressure signal as well the other signals to be transmitted after one in memory 23 stored program converted into a broadcast signal and supplied to a transmission output stage 25. Of the Transmit output stage 25, the signal on the antenna 26th transfer.

The antenna 26 consists of a ferrite core, which with Copper wire is wrapped. Has proven to be particularly cheap an inductance of the transmitter coil in the range between 10 and 50 mHenry proven.

Different modes of operation of the transmitter are now 3, in which the various Functional modes of the transmission part plotted over the time axis 40 are.

In time segment 41 is in the left part of the figure the transmitter in stand-by mode. In this mode the signal conditioning circuit is caused to to carry out a pressure measurement at certain intervals, what is characterized by columns 42. As preferable The time interval here is approximately 5 seconds surrender. The microprocessor 22 is between two Measurements always switched to a stand-by mode in which he uses very little energy. That’s it possible, the transmitter part with a typical usage profile for about 5 years with a lithium battery operate.

The start signal for the pressure measurement comes from the timer 21 of the transmitting device. The microprocessor 22 is then activated and the pressure by means of the pressure sensor 7 measured.

As soon as a certain switch-on criterion is fulfilled, the transmission device from stand-by mode to transmission mode switched. Various switch-on criteria can be used Criteria are used. Has been particularly advantageous it turned out to be the result of two successive Compare pressure measurements and if the pressure rises to switch to transmit mode. The switch-on criterion is preferably such that the transmission mode is switched on if within 5 sec an increase in pressure from below 5 bar to e.g. 30 bar or above is determined. This increase is in achieved in any case if the user of the breathing apparatus Shut-off valve 6 of bottle 5 opens and thus the Pressure sensor 7 applied with the bottle pressure. Random pressure fluctuations, e.g. through temperature changes, Changes in height etc. are not enough to meet this switch-on criterion.

After switching on takes place in time period 43 initially a so-called identification change mode or Pairing mode takes place, which will be explained later.

The identification change mode is followed by the actual one Normal mode in period 45, which is the real one Represents the use phase of the device. As in FIG. 3 is shown schematically, change in this mode a measurement interval 46 and a transmission interval 47 from. It has proved to be cheap, even during normal mode with a time interval of the pressure measurements of 5 sec to work. After the recording of each measured value is then generated and transmitted by the microprocessor the transmission output stage 25 fed to the antenna 26.

The time interval between the pressure measurement and the transmission of the signal is not constant, but is replaced by the Random microprocessor within a predetermined time range varies. The sending of the However, the signal always occurs before the next one is recorded Measured value. This time variation has the advantage that two operated simultaneously at a short distance Monitoring devices using various breathing apparatus monitor a collision of transmitted signal values can only happen randomly. Would be the time interval between Measuring interval and sending interval always the same unfavorable constellation arise that that of two Values broadcasted values with each other for a long time collide.

As soon as a specified switch-off criterion is met, the transmitter is switched back to standby mode, what is shown in period 49. The Switch-off criterion exists if for a predetermined one Number of measuring intervals no longer decrease in pressure is detected.

The signal transmission from the transmitting device 2 to the receiving device 3 takes place by means of an electromagnetic radio wave of constant frequency. The quartz-controlled timer 21 is used to control the transmission frequency. Since the frequency of the quartz crystal is 32,768 Hz, the structure of the transmission part is simplified if a frequency is used which is derived from this frequency with the divider 2 ⁿ . The frequencies 32,768 (n = 0), 16,384 (n = 1), 8,192 (n = 2) and 4,096 (n = 3) are therefore particularly preferred. Experiments have shown that particularly good data transmission under water is achieved by using a carrier frequency of 8,192 hertz.

In the interest of interference-free data transmission the data signals to be transmitted in the transmitting part 2 digital coded. To transfer the digital values, there is in the State of the art various processes in which the Frequency, amplitude or phase of the carrier signal to be changed.

A known method that is also used for the monitoring device of the type shown could be used the frequency change of the transmission signal with the so-called Frequency Shift Keying ''. With this procedure the Bit information contents 0 and 1 different frequencies assigned. However, this means that 2 frequencies have to be transmitted what increases the effort on the sender and receiver side.

The best option for the transmission has been Influencing the phase position with the so-called "phase Shift Keying "(PSK) has been proven, with the present Embodiment another special variant of the PSK process is used, namely the "differential phase Shift Keying "(DPSK).

With this method, the transmission signal experiences one Phase shift when a 1 is transmitted; should be a 0 the send signal remains unchanged. Because with this method the first bit of the transmitted bit pattern contains an uncertainty, it must not be used as an information carrier serve.

An example of this digital encryption is in Fig. 4 shown. The diagram 60 is over a time axis 61 and a number axis 62 a bit pattern consisting of bits 011010011 ....

In diagram 64, 65 is above the scaled time axis and the voltage axis 66 a voltage signal 67 plotted, which has a constant frequency has, but by the above-described DPSK modulation the bit pattern is impressed as a phase change is.

Within each transmission interval there is a signal sequence 5, which, as shown in FIG. 5, consists of a Preamble, the identification signal, a data block and a postamble is set up. The preamble serves the Receiving device the synchronization to the sent Enable signal. The identification code contains the transmitter-specific identification. The identification code the actual one to be transferred closes Data block. The data block always contains the measured pressure value, but can be at a preferred Embodiment also contain a temperature value, which is detected by a corresponding temperature sensor. It is also possible to e.g. from the measurement of the Pressure signal derived respiratory rate in this data block transferred to. Of course, others can also Data will be transferred if this is specific Use case is of interest. This is followed by the Postamble, which is used, among other things, for error correction.

In the illustrated embodiment, this includes 16-bit synchronization interval, the identification code 24 bits, the data block 32 bits and the postamble 4 bits. So each signal is 76 bits long.

Experiments have shown that it is suitable for the DPSK is favorable, a total of 8 periods of the carrier frequency per bit to broadcast at 8196 Hertz. This results in a total broadcasting time of 0.976 msec / bit or a total signal duration of approx. 74 msec.

With reference to Fig. 7, the structure of the receiving part described.

The receiving part 3 is separate from the transmitting part in one Plastic housing 70 housed and has none Connection mechanical or electrical Lines with the transmitter part 2. The plastic housing 70 is with electrically non-conductive oil, silicone or the like filled and has a battery 71 to the electrical and electronic components with electrical To supply energy. On the housing 70 is also a flexible bracelet (not shown) arranged that it allows the user to use the receiving part as one Attach wrist watch to wrist.

The housing is designed to withstand water pressure too withstands the greatest depths that can be reached by divers and has on its outer surface facing the water no movable electrical switching devices. Around to be able to put the device into operation and in pairing mode however, there are several to confirm the assignment electrically conductive metal pins 73 embedded in the housing, that of the diver e.g. to be bridged with his fingers can what as the receiving part under certain circumstances Switch event is interpreted.

The receiving part has one or two ferrite antennas 80 on, as shown schematically in the figure. The received signal is first a signal processing and Amplification stage 81 supplied to which a Digitizing stage 82 connects. Both components correspond usual design.

The digital signal is fed to a comparator 83. This comparator determines whether the received and processed signal the identification signal or the Identification control signal contains. Is that the case, the signal is fed to a microprocessor 85 which, controlled by a stored in a memory 86 Program that takes over further processing.

The use of the upstream comparison stage has the Advantage that the microprocessor 85 only with the signal is applied when it is established that the individual Receiving device is addressed.

The timing of the receiving part is carried out via a Timer 84.

The data derived from the received signal as well if necessary, further data are shown on the display 87 Users displayed. The display 87 is behind one transparent area in the wall of the housing 70 of the Receiving part 2 arranged. The in the bottle 5 prevailing pressure and preferably also the remaining breath time is displayed. To do this, a further pressure sensor 89 is required, the respective Measures ambient pressure. The remaining breath will be determined by the microprocessor from the pro Time unit measured pressure drop taking into account the current air consumption is determined from the ambient pressure becomes. The air consumption can either be short past time or over a longer period of time be averaged to obtain realistic values. Out of it then the expected time to complete Extracted air extraction.

The respective data are shown on the display as long as until after a new measurement and the transfer of the Values new data are determined.

The receiving device also has a schematic only Switching device 88 shown with those already mentioned Metal pins 73 on. The metal pins 73 can also in greater distance from each other or at different Sides of the case can be arranged to prevent accidental To prevent contact bridging.

The following describes how the assignment or the pairing of transmitter and receiver within the Identification change mode is made.

As already explained, each broadcasting part will be broadcast on the Manufacturing an identification signal that is assigned is only awarded once. With the above In this embodiment, a 24-bit signal is used resulting in a total of 16.7 million different ones Identification opportunities arise. Because of this high number ensures that there are never two transmission parts with same signal exist.

The identification signal of the transmitting part is in one Read-only memory area of the memory 23 of the transmitting part 2 filed. It is also possible to in the identification signal store a RAM memory area; in this case but the signal e.g. through simultaneous use as Manufacturer number otherwise fixed in the device, so the signal is correct again when changing the battery can be read.

The identification change mode is started every time when the transmitter is put into operation. This happens, as explained above, preferably by a fixed switch-on criterion, e.g. turning up the Device valve 6 of the bottle 5. The transmitter part then goes in the identification change mode and sends, as in 6 shows a signal which consists of a preamble, an identification control signal, the actual identification signal and there is a postamble. At the The preamble is 16 bits, the postamble 4 bits and the identification control signal and that Identification signal each 24 bits long.

The identification control signal is from all receiving parts of the corresponding series understood. Once a Receiving part receives this signal, it is over the Microprocessor in the identification change mode switched. The processor then asks on the display whether the identification signal of the transmitting part is accepted shall be. This is done by the user via the switching device 88 confirmed by means of the metal pins 73, that is Identification signal of the transmitter part adopted and in Memory 86 as an identification comparison signal saved.

The control program of the stored in the memory 86 Receiving part can be designed so that the receiving part, once it has the identification control signal of the Receiving part in identification change mode, checks whether its stored identification comparison signal with the identification signal of the Transmitting part matches. If so, it can Receiving part then indicate that it is on this transmitting part is set so that the user knows that the two Devices are assigned to each other.

To avoid accidentally assigning devices, indicates the identification change mode in the embodiment several security levels.

The first stage is the coupling of the beginning of the Identification change mode to the switch-on criterion of the transmitting part. The identification change is only ever immediately after the switch-on criterion occurs performed. This reliably prevents a Identification change during normal use of the Devices is started.

The second part of the security level is used by the receiver a corresponding device an energy measurement of the in Identification change mode received signal carried out. The program of the receiving part is so designed that whenever the identification control signal is received, an energy measurement of the Overall signal is carried out. Only when the transmission energy exceeds a certain limit is one Assignment possible.

The transfer of energy from the transmitting part to the receiving part depends, as is known, on the distance and, to a considerable extent, also on the respective alignment of the two antennas to each other. Only if the devices are spatially and angularly are arranged in a certain way to each other, the maximum energy absorbed by the receiver. The The limit value for energy measurement is therefore chosen so that an assignment can only take place if send and Receiving part are arranged at a small distance from each other and also a given angular orientation to each other. To the angular assignment too the antennas of the transmitter and Receiving part preferably so in the respective housing arranged that the maximum energy at a parallel or T-shaped arrangement of the devices to each other results. To rule out coincidences here, too the transmission of the identification control signal several times repeated and only then of sufficient signal energy assumed when the measured value at a certain percentage of the transmissions above the Limit is.

Finally, the user still has to, and this represents the represents the next security level, the switching device 88 press to confirm the identification change. For this, e.g. the three metal pins in a way used that in the identification change mode only two may be bridged. This excludes that an identification assignment under water (in this Case, all three metal pins would be electrically connected) happens. It is also possible to have three metal pins in the Way to use that first a first pair and then a second pair must be bridged.

1. Sende- und Empfangsteil praktisch unmittelbar nebeneinander in definierter Winkellage angeordnet sind;

2. in diesem Zustand das Absperrventil der Luftflasche geöffnet wird;

3. und die Identifikation durch den Benutzer manuell bestätigt wird.

An assignment only takes place if

1. transmitting and receiving part are arranged practically immediately next to each other in a defined angular position;

2. In this state, the shut-off valve of the air bottle is opened;

3. and the identification is manually confirmed by the user.

The following describes how the one shown Receiving device the plausibility of the received data checked.

As stated at the beginning, the monitoring device should if possible never, not even at short notice, wrong values Show. Because of the wireless transmission it can however, the reception of the whole while a transmission interval transmitted signal or parts of the signal, e.g. by strong movements of the user or the like is impaired.

When two transmitters are close to each other work, it could also happen that the send two broadcast parts at substantially the same time, so that the signals overlap and therefore no longer must be clearly identified.

Furthermore, even if this is unlikely, happen that by overlaying different signals a pattern is created for a short time, which is the identification signal happens to match.

This problem can be countered by whenever that The signal was not recorded absolutely correctly corresponding display is suppressed.

In the embodiment shown is an additional Security measure a plausibility check provided to rule out any danger of a false report. The plausibility check is carried out via the Calculation of the expected pressure drop in the bottle of the breathing apparatus by the microprocessor of the receiving part.

When using the breathing apparatus essentially breath is taken continuously, and the pressure in the Bottle 5 drops accordingly continuously, from which the current air consumption is determined. Based on air consumption is calculated by the microprocessor like the Pressure drop in the bottle with a continuous Air extraction should decrease further. With every pressure measurement it is then determined whether the newly measured pressure is plausible compared to the previously measured pressure values. If this is the case, the new pressure value is shown on the display displayed. Is the pressure value not plausible, or will no signal or no complete signal in the predetermined Time interval received, then either no pressure value is displayed, or the last measured pressure value is displayed displayed, but with an additional symbol or e.g. a blinking indicator indicates that this is is the result of a previous pressure measurement.

If no pressure signal is received for several measuring intervals, or the signal cannot be clearly identified due to interference, this ad will continue until an im Microprocessor 86 control program set Timeframe is exceeded. From this point onwards assumed that reliable pressure values no longer are present and the calculation of air consumption set. This is shown in the display 87 accordingly identified.

Are pressure signals received again by the Transmitting part assigned to the receiving part originate, so these are displayed, but with an additional symbol, e.g. With a flashing light or the like, by which the user is informed that a plausibility check of this Values is no longer possible.

In a further embodiment of the invention Monitoring device, which is shown schematically in FIG. 8 is shown, the monitoring device with a Decompression calculator combined. The decompression calculator could be with the sending device as well as with the receiving device be arranged. However, as with shown embodiment, the receiving part of the Monitoring device and the decompression computer in one housing united together as the decompression computer then also in the event of a failure of the transmission device remains in function.

Decompression computers of the type in question here known in the art. The patent applicant has such devices, for example, in large numbers in 1989 in Europe, USA, Japan, Australia and many other countries e.g. under the name "Aladin pro" expelled. With such decompression computers the current ambient pressure, which is a measure of the diving depth is, and the entire dive time over a corresponding Pressure measuring device and a time measuring device detected. With These input values are based on one in a memory stored program using a microprocessor Saturation and desaturation behavior of a certain Number, e.g. six or sixteen different tissues simulated. By comparing the burden of The computing unit determines which tissue Tissue is decisive for decompression, the so-called Guide fabric, and then determines the number, the depth and the respective duration of the necessary decompression stages. The diver will see the on a display total diving time, the current diving depth, each next decompression stop and the entire duration displayed that is required to work with a particular prescribed ascent rate and the Decompression steps to reach the water surface. Furthermore, the decompression computer with memory devices provided, a so-called log book, in which the Dive profile from previous dives saved is, so that the diver after leaving the water the respective diving times etc. Furthermore is such a decompression computer with a device to measure the air pressure before diving to thus also for lakes that are at a higher altitude than the Sea level to be operational and to keep up with fluctuations in air pressure not to be included in the measurement result.

It is possible to receive the receiving part of the invention Monitoring device and the computing unit for the Combine decompression calculation so that both controlled by a common microprocessor.

The programming and construction, however simplified if instead a solution with two Microprocessors is applied.

The embodiment shown in Fig. 8 of the invention Monitoring device works with one Transmitting part, as explained in relation to FIG. 2 and is therefore no longer shown in FIG. 8. The Receiving part has a pressure-resistant, non-magnetic Housing 100 in which, as by the dash-dotted line Is indicated area, the receiving device 103 and the Decompression calculator 104 are arranged together. The Housing is oil filled and has an internal pressure that is the same is the pressure of the water surrounding the housing. The Dimensions of a sample of this case that is to be worn provided on the wrist is approx. 75 mm (length transverse to the arm direction) and about 75 mm wide, along the Poor measured. The housing has a thickness of approx. 20 mm.

The receiving part 103 is as described above constructed and has an antenna 110 and a first Microprocessor 112 with a memory 113. The in essential components serving the signal processing are summarized schematically in component 111.

The decompression computer has a microprocessor 120 with a memory 121 for program and data. The Pressure of the surrounding water is measured by a pressure sensor 125 recorded. The remaining electrical components, such as Timers etc. are summarized schematically in component 127.

As common components are at least the Power supply battery 130, one in the Housing wall recessed display 132 and a switching device 134 provided with four metal pins 136.

As further common components, a common one Display control device and a common timer and the like can be used.

• der Druck in der Atemluftflasche in bar oder psi;
• die verbleibende Zeit zum Aufenthalt auf der jeweiligen Tiefenstufe, unter Berücksichtigung der für den Aufstieg erforderlichen Zeit (remaining air time) in min oder mit einem Symbol, z.B. einer auslaufenden Sanduhr;
• die gesamte Tauchzeit seit Eintritt in das Wasser;
• die aktuelle Tauchtiefe;
• der nächste Dekompressionshalt und die dort zu verbringende erste Dekompressionszeit;
• die Gesamtauftauchzeit;
• die maximal getauchte Tiefe;
• die momentane Aufstiegsgeschwindigkeit.

The microprocessors are each controlled by their own program, but exchange data via a schematically indicated data line 138. From this, the following data are determined and shown on the display 132 with numbers and / or symbols:

• the pressure in the breathing air bottle in bar or psi;
• the remaining time to stay at the respective depth level, taking into account the time required for the ascent (remaining air time) in minutes or with a symbol, eg an expiring hourglass;
• the total diving time since entering the water;
• the current diving depth;
• the next decompression stop and the first decompression time to be spent there;
• the total ascent time;
• the maximum depth immersed;
• the current ascent rate.

• ein Signal, z.B. das Blinken der Druckanzeige, das anzeigt, daß der aktuelle angezeigte Flaschendruck nicht über die Luftverbrauchsprognose kontrolliert ist, da die Verbindung zwischen Sendeteil und Empfangsteil längere Zeit unterbrochen war;
• eine Anzeige für eine kurzfristige Unterbrechung der Verbindung Sendeteil und Empfangsteil;
• ein Signal, wenn die maximale Aufstiegsgeschwindigkeit den erlaubten Wert überschreitet (dieser Wert kann durch in kurzem zeitlichen Abstand erfolgende Druckmessungen mit dem Drucksensor 125 bestimmt werden).

In addition, the following functions or malfunctions can be indicated or output by the flashing of the corresponding values or by additional visual and / or acoustic warnings:

• a signal, for example the flashing of the pressure indicator, which indicates that the current cylinder pressure displayed is not controlled by the air consumption forecast, since the connection between the transmitter and receiver has been interrupted for a long time;
• a display for a brief interruption of the connection between the transmitting part and the receiving part;
• a signal when the maximum ascent rate exceeds the permitted value (this value can be determined by pressure measurements with the pressure sensor 125 taking place at short intervals).

Furthermore, the monitoring device can according to this Embodiment coupled with ads that are first become visible after leaving the water, e.g. a Warning sign in the form of an airplane that the diver indicates that the use of an airplane is not yet is possible again, a logbook display etc.

The decompression data are, as described above, from the microprocessor 120 via the simulation of the behavior determined a certain number of tissue types. The allowable residence time at a certain depth by e.g. iterative approximation, by the pre-calculated time that the air supply still sufficient in the remaining stay and in the Total surfacing time that is required to expire the time of stay emerging from this depth is divided.

In addition to the input variables pressure and time, the calculated air consumption in the decompression calculation be taken into account. Because air consumption is a measure of that physiological work performed by the diver, can, according to the research results of the Diving medicine, the influence of physical work performance on the decompression times are taken into account.

Claims (33)

1. A monitoring device for a portable breathing apparatus having

   a pressure measuring means which detects the pressure in one or more pressure containers of the breathing apparatus by means of a pressure sensor and emits an electrical pressure signal which is representative of the pressure;

   a transmitter which receives the pressure signal emitted by the pressure measuring device and emits a transmission signal corresponding to said pressure signal;

   a receiver allocated to said transmitter and which is to be portably carried by the user for receiving the transmission signal emitted by the transmitter;

   a microprocessor means arranged in the receiver controlled by a program which is stored in a memory arranged in said receiver, whereby said microprocessor means calculates the pressure value as measured by the pressure measuring means from the received transmission signal;

   a display device which displays data as digits and symbols and which is coupled with said receiver for displaying the calculated pressure value;
   characterized in that

   the transmitter comprises a control means which induces that the transmission signals are emitted at intervals,

   said control means further inducing that the temporal interval between a pressure measurement and a transmission of the transmission signal is not constant,

   the transmitter comprises a signal generating means which generates an identification signal which is characteristic for the individual transmitter and unambiguously identifies same,

   the control means induces said identification signal to be transmitted at least once within each transmission interval,

   the allocated identification comparison signal corresponding to each associated individual transmitter is stored in the memory of the receiver, the receiver comprises a comparison means which employs this identification comparison signal to test whether a received signal contains the allocated identification signal of the corresponding transmitter, and

   that the receiver only calculates and displays a pressure value from a received signal when the identification signal received by the receiver matches the identification signal stored in the corresponding transmitter.
2. Monitoring device according to claim 1, characterized in that
   a converter is provided which encodes the signals to be transmitted by the transmitter into digital form.
3. Monitoring device according to claim 1 or 2, characterized in that
   at least the control means and the signal generating means of the transmitter are combined in a first microprocessor means which is controlled by a program stored in a memory.
4. Monitoring device according to at least one of claims 1-3, characterized in that
   the identification signal is stored in the transmitter as a digital number sequence of n bits and that the identification comparison signal is likewise stored in the receiver as a digital number sequence of n bits.
5. Monitoring device according to at least one of claims 1-4, characterized in that
   the identification signal stored in the transmitter and/or the identification comparison signal stored in the receiver is/are variable in order to match the identification signal of the transmitter and/or the identification comparison signal of the receiver to one another.
6. Monitoring device according to claim 5, characterized in that
   the signal generating means of the transmitter generates an identification control signal, that an identification control comparison signal is stored in the memory of the receiver, and that the comparison means switches the receiver into an identification signal change mode as soon as said comparison means recognizes that an identification control signal emitted by the transmitter is identical to the identification control comparison signal stored in the receiver.
7. Monitoring device according to claim 6, characterized in that
   the transmitter has a first detector means which recognizes the occurrence of a predetermined condition and induces the transmitter to switch from transmission mode, in which at least the pressure signal and the identification signal are transmitted, into an identification signal change mode in which an identification control signal and the identification signal are transmitted.
8. Monitoring device according to claim 7, characterized in that
   the pressure signal measured by the pressure measuring means is fed to the first detector means and is recognized by said first detector means as a predetermined condition when the pressure measured by the pressure measuring means rises by a predetermined value within a predetermined period of time.
9. Monitoring device according to at least one of claims 6-8, characterized in that
   the receiver has a signal power measuring means which measures the energy of the signal received from the transmitter at least when the comparison means ascertains that an identification control signal emitted by the transmitter is identical to the identification control comparison signal stored in the receiver.
10. Monitoring device according to at least one of claims 6-9, characterized in that
    the receiver comprises a manually actuable switching device, and that an identification signal received during identification change mode is only stored by the receiver if this manual switching device is actuated.
11. Monitoring device according to claim 10, characterized in that
    said switching device comprises electrical contact pins made of metal which are led through an electrically non-conductive section of the receiver housing and can be touched from the outside.
12. Monitoring device according to claim 5, 6, 9 and 10, characterized in that
    the receiver only stores an identification signal received during identification change mode when the energy of the received transmission signal lies above a specific predetermined value and if the switching device is actuated.
13. Monitoring device according to at least one of claims 1-12, characterized in that
    transmission of the transmission signal from the transmitter to the receiver ensues by means of ultrasonic sound.
14. Monitoring device according to at least one of claims 1-12, characterized in that
    transmission of signals from the transmitter to the receiver ensues by means of electromagnetic waves (radio waves).
15. Monitoring device according to claim 14, characterized in that
    the frequency of the electromagnetic waves in the long wave range preferably lies between 5 and 100 kilohertz, especially preferably between 5 and 50 kilohertz and most particularly preferred between 5 and 15 kilohertz.
16. Monitoring device according to claim 14 or 15, characterized in that
    the transmission of data transpires via a change in the phase position of a sinusoidal signal (phase shift keying) and preferably via a differential change in the phase position (differential phase shift keying).
17. Monitoring device according to at least one of claims 1-16, characterized in that
    at least 4 bit strings, each comprising a predetermined number of bits each, are transmitted during each transmission interval, whereby the first bit string is a preamble which enables synchronization of the receiver to the transmitter, the exemplary second and third bit string is a data sequence which is representative for the measured pressure signal, contains the identification control signal respectively, and an exemplary fourth and last bit string is a postambel concluding each transmission interval.
18. Monitoring device according to at least one of claims 1-17, characterized in that
    the transmitter has a timer unit which is so controlled such that the pressure measuring means measures the pressure in predetermined, fixed intervals of time.
19. Monitoring device according to claim 18, characterized in that
    the value determined during pressure measurement is converted to a transmitting signal and is transmitted prior to the next pressure measurement taking place, and that a random circuit is provided to induce that the temporal interval between the pressure measurement and the transmitting of the measured pressure signal ensues in accordance with a random process.
20. Monitoring device according to claim 18 or 19, characterized in that
    the transmitter comprises a second detector means which recognizes an occurrence of a specific event and which, upon the occurrence of such an event, switches the transmitter from a passive standby mode into an active transmission mode, and that a further third detector means is provided which recognizes that the measured pressure value does not change over a predetermined number of successive pressure measurements and which switches the transmitter from active mode into passive mode.
21. Monitoring device according to at least one of claims 2-20, characterized in that
    preferably by means of the microprocessor means of the receiver, the expected decrease in pressure, the air supply in the pressure container respectively, is extrapolated from the current rate of consumption of said air supply.
22. Monitoring device according to claim 21, characterized in that
    upon a brief interruption occurring in the connection between the transmitter and the receiver, the subsequent newly received measured pressure value is compared with the extrapolated pressure value and displayed should the extrapolated expected pressure value and measured pressure value differ by a predetermined amount.
23. Monitoring device according to claim 21 or 22, characterized in that
    the amount of time that the given air supply is expected to last is determined from the extrapolated current rate of air consumption and, when necessary, displayed.
24. Monitoring device according to at least one of claims 1-23, characterized in that
    the receiver as well as the transmitter are each arranged in a pressure-tight, preferably oil-filled housing so that the monitoring device can be employed underwater.
25. Monitoring device according to at least one of claims 1-24, characterized in that
    the receiver and display device are arranged in a common housing which is secured with fastening means to the arm or around the wrist of a user.
26. Monitoring device according to at least one of claims 24 or 25,
    which is especially intended for the purpose of being brought along during a dive
    characterized in that
    the receiver is coupled to a decompression computing unit which itself is connected to a second pressure measuring means as well as to a timer and, by means of a predetermined program stored in a memory of said decompression computing unit, calculates, taking into consideration times spent at different diving depths, how long the user requires to reach the surface of the water without the risk of decompression sickness, whereby the total time necessary for resurfacing and/or the next decompression stop and the length of time which is to be spent there and/or an exceeding of the maximum allowable speed of ascent, are all displayed to the user.
27. Monitoring device according to claim 26 and 21, characterized in that
    the microprocessor means of the receiver, respectively the decompression computing unit, calculates and displays, based on extrapolated times, the length of time remaining in the air supply as well as, based on ascertained overall resurfacing time, the amount of time which the diver may still remain at a respective current diving depth.
28. Monitoring device according to claim 26 or 27, characterized in that
    the receiver and decompression computing unit have separate microprocessor means.
29. Monitoring device according to claim 26 or 27, characterized in that
    the receiver and decompression computing unit have a common microprocessor means.
30. Monitoring device according to at least claim 3, or claim 3 and one of Claims 1-29, characterized in that
    said first microprocessor means of the receiver furthermore executes at least partially the functions of said pressure measuring means and/or said converter and/or said first and/or said second and/or said third detector means and/or said random circuit via the program stored in the memory.
31. Monitoring device according to at least claim 9, or claim 9 and one of Claims 10-30, characterized in that
    said microprocessor means of the receiver executes at least partially the function of said signal power measuring means via the program stored in said memory.
32. Monitoring device according to claim 26 or 27, characterized in that
    the result of an air consumption measurement is fed to the decompression computing unit as a further input variable so that the influencing factor of air consumption as a measure of the physiological efficiency of the diver is taken into consideration in the calculation of decompression parameters.
33. Method for monitoring a portable breathing apparatus having a gas-oxygen mixture within a pressure container, comprising a monitoring device having a pressure measuring means, a transmitter and a receiver, whereby the receiver and transmitter each are disposed with a microprocessor means,
    characterized in that
    said transmitter transmits the measured pressure values and, when necessary further data, at transmission intervals, whereby the temporal interval between the pressure measurement and the emitting of a transmitter signal is not constant and that an identification signal characteristic of an individual transmitter is likewise emitted with each transmission interval, whereby the transmission ensues in digitally coded form and the receiver compares said transmitted identification signal with an identification comparison signal stored in a memory of said receiver and induces that the transmitted pressure data and, when necessary other data, is only further processed when the identification signal emitted by the transmitter and the identification signal stored in the receiver are identical, and whereby said identification signal stored in the transmitter and/or said identification comparison signal stored in the receiver is/are variable in order to match said identification signal and/or said identification comparison signal of the transmitter and/or receiver to one another.

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