DE3125366A1 - Capacitive instrument transformer - Google Patents

Abstract

The subject-matter of the invention is a) a method for measuring very small capacitance differences (for example differential capacitor), particularly suitable for measuring pressure by means of diaphragms, but also for other measuring methods in which an electrically conductive plate is moved. The excursion of the plate can be very small. Due to the interconnection according to the invention of a differential capacitor or of two single capacitors, two monostable flip-flop stages and an exclusive OR gate, an output signal is produced, the length of which is proportional to the capacitance difference; b) a method which allows the bending-through of a pressure measuring diaphragm to be avoided and thus to measure independently of its mechanical characteristics. The bending-through is compensated for by electromagnetic forces which are applied according to the invention by two electromagnets attached on both sides of the diaphragm and which operate in accordance with the digital principle, that is to say they consist of a number of individual magnets of different strength which are switched on or off in combination, their switching states at the same time representing the digital measurement signal for the magnitude of the pressure; c) an apparatus composed of a) and b) for measuring minimum pressure differences (e.g. "Warburg manometry").

Description

description

The invention allows very small day changes of a flat metallic or metallized object, such as a measuring membrane, reliably, very accurate, very sensitive and very quick to detect, with the change in position can move in orders of magnitude down to 10 mm and less and the temporal Resolution in the order of magnitude of lo - 10 5.

Changes in position of this magnitude are very important during the measurement small pressure differences, for example with the so-called "War castle manometry" using membrane in front; the specified temporal resolution is required when there are pressure changes the kinetics of rapidly running physiological-chemical processes can be registered or when sound is to be converted into electrical signals (microphone).

The pressure measurement by means of a membrane is generally by the mechanical properties the membrane itself affected; especially with the Warburg manometry " the requirement that the volume in the measuring space should remain constant. That is why at One embodiment of the invention avoids the deflection of the membrane.

The pressure measurement by means of an electrically conductive membrane with two solid plates forming a differential capacitor is known. (e.g. Niebuhr, Physical Measurement Technique Vol. I and II). The capacitance difference is measured iQa. with an alternating current stored measuring bridge by measuring the capacitive Reactance. However, this method has several disadvantages: by a high To achieve resolution, one has to work with high frequencies, which is very susceptible to interference by interference fields, the elimination of which requires a great deal of effort. Non-linearities must be taken into account when measuring with the non-tuned bridge be taken, an automatic tuning of the bridge requires a lot of effort with a relatively low sensitivity and high susceptibility to failure.

As an aid, it was suggested that the capacitors should be part of the process of oscillating circuits, and changing their resonancei.c3.-nscl-, aften to measure what, however, a very high effort caused and by a significant malfunction is accompanied, so that the aim of this procedure is not generally prevailed.

Also the measurement of pressure with a simple plate capacitor and an astable multivibrator has already been proposed (DT-AS 23 18 281 B2, DE-OS 28 53 504 A1); In these devices, the astable multivibrator generates a square wave signal, its duty cycle and / or frequency due to the change in capacitance of the simple Capacitor is changed. The square wave signal can be measured directly with an analog measuring device (Effektivtqert) or digitally measured via an additional circuit.

However, these devices have the disadvantage that they are with a simple capacitor work and on the generally recognized in pressure measurement technology Do without the advantages of the differential capacitor (e.g. Niebuhr, physical measurement technology), and in addition the output signal is a measure of the capacitance of the capacitor and not directly for the pressure (if the pressure difference = 0, the output signal is not 0>.

In addition, these arrangements have an unfavorable temperature behavior on (temperature dependency is not compensated), and the resolving power is small due to the influence of stray capacitances. Furthermore, through the use of the astable multivibrator or its modifications, the temporal resolution limited because, for example, at a fixed frequency and a change in the duty cycle due to the capacity, only part of the cycle time is actually used for the measurement will.

The problem with all pressure measurements using a measuring membrane is that the measurement is influenced by the mechanical properties of the membrane, which is expressed by the hysteresis, the temperature drift and in non-linearities. These effects are greater, the greater the deflection of the membrane.

It has therefore been proposed devices that the membrane through Use of external forces to bring them back into their resting position, e.g. 13. by electrostatic or electromagnetic forces (e.g. Kohlrausch, Practical Physics, Vol. I). These Arrangements, however, provide extremely precise control of the restoring forces and an equally exact zero indicator ahead. The control was with analog circuits tries; Even with a high level of Allfwant1 was due to temperature sensitivity, Rush, Asymmetries and tendencies to oscillate apparently did not achieve a satisfactory result, also due to the lack of a suitable zero indicator.

Another suggestion for solving the problem can be found in the DE-OS 29 40 674; Here the control of the magnet takes place with the help of an electromechanical Switch.

In the rest position, the membrane closes the switch, it is through If the pressure is deflected, the switch opens and the magnet comes into action until the Switch is closed again (shown in simplified form). Repeated this game running.

The arrangement has the disadvantage of a certain inertia and a high Susceptibility to failure because the switch runs in time with the cycle (high) frequency is opened and closed. With capacitive pressure measurement by means of diaphragms The clamping of the membrane is also a problem. The membrane should on the one hand be gas-tight be clamped, on the other hand, a certain radial mobility of the membrane must be be guaranteed because of the diameter reduction in the deflection and the The membrane should be insensitive to shocks and temperature influences. aside from that interference fields should be kept away from the Di to its differential capacitor.

Proposals for clamping the membrane can be found in OS DE 27 55 306 A1, DE 3002 268 A1 and DE 30 11 269 A1.

Devices of this type tighten the membrane more or less tightly a. As a result of the deflection, however, a certain radial movement is forced. This leads to the fact that with a firmly clamped membrane, the steering from the one hand depends on the (non-reproducible) strength of the restraint, on the other hand A hysteresis can arise from the fact that the diaphragm with increasing deflection slides out of its guide and, with decreasing deflection, back into its Guide must slide back, the membrane iva.

slides out more easily than back again. Further can temperature changes in the case of fixed clamping to tension in the membrane and at the clamping points to lead.

For the so-called Warburg manometry "there was no such thing at all useful method for automatic pressure measurement. Still today happens at dicoeS Met; de, diu to record chemical and physiological-chemical as well as physical-chemical processes due to gas exchange reactions in the area applied in scientific research and medicine, pressure measurement manually with the help of U-tube manometers to Marburg.

These are capillary pressure gauges with the help of a Hose that connects the two legs, and a pinch cock the height the liquid columns can be changed. The screw is used for each measurement the pinch cock which brings a column of liquid to a defined height, then read and write down the height of the other column. To make matters worse, that the measurements must often take place in the dark, the device for improvement the gas exchange between liquid (in which the sample to be examined located) and gas space must be shaken and often 12 measuring points at the same time must be read.

The procedure is thus extremely time-consuming, involves a large one subjective error when reading the pressure gauge, has an often inadequate timing Resolution (at best reading in 1-minute intervals) is often inadequate Sensitivity (height differences below 1 mm WS are hardly detectable) and makes one great effort is required in evaluating the measurement results, since all of them have been read off Results around the values of a control manometer (so-called thermobarometer), the temperature and changes in atmospheric pressure must be detected and corrected.

Despite its recognized great scientific and medical benefits Measurements, this method is very in the background for the reasons mentioned moved, although there are numerous detailed application examples of the "Warburg manometry" there.

Previous attempts to automate the "Warburg manometry" have did not lead to success. The attempt to read the pressure gauges optoelectronically had to be made fail because of the high mechanical effort involved. The measurement on piezoelectric or piemoresist.iver base showed a hollow temperature sensitivity and a poor reproducibility, mature the measurement using strain gauges criticism of the insufficient sensitivity.

The problem solved according to the invention was to develop a room device, which combines a high sensitivity with a high resolution and reliability, that is insensitive to the unavoidable shaking of this method, that shows a low temperature sensitivity and an automatic registration and evaluation of the measurement results, if possible with the help of data processing systems, allowed.

It should also be possible to change the volume as a result of the deflection to avoid the membrane, since the pressure according to the gas laws also depends on the volume and even a minimal change in volume for pressure measurements in the order of magnitude the "Warburg manometry" has a considerable influence on the measured pressure.

In order to enable broad application of the method, the System as simple as possible and, above all, reliable, whereby the difficulty was to achieve very small pressure differences (corresponding to 0.1 mm WS and including) to measure accurately and safely, with the system also by non-skilled personnel if possible should be operable.

According to the wide range of applications of the "Warburg manometry" should the sensitivity can vary within very wide limits and in a simple manner as both very small changes in pressure (e.g. fluctuations in the respiration of insect larvae -lmm WS per day) as well as larger pressure changes (carbon dioxide releases from Parts of plants) can occur depending on the area of application.

The object was achieved according to the invention by initially using an electronic Circuit was developed which allowed capacitance differences to be measured very precisely and to be recorded reliably, since the only solution to the task is to measure with the aid of a differential capacitor could be considered.

The secure recording of small changes in capacity made it possible to keep the deflection of the membrane very small (e.g. max. 5x1O-2mm at approx. 70mm Diameter). This low deflection, in conjunction with the measure that the cough plates can be smaller than the membrane, a very good linearity the change in capacitance during deflection and also allows the use of <; a relatively thick Meinbran (ca, O, lmm), what the measuring device gengem makes the violent shaking movements largely insensitive. This attribute is supported by the suspension of the membrane between two O-rings (see drawing 1). This suspension also ensures a largely smooth radial mobility the membrane, which significantly reduces hysteresis and temperature insensitivity and also has the advantage of a perfect seal.

The defined distance between solid plates and membrane is through the exchangeable intermediate ring, the one with spacers of different thicknesses can be supplemented.

By simply changing the ring and the washers thus the distance between the plates and thus the sensitivity and the measuring range are very simple to be changed.

There is another possibility of changing the sensitivity in the use of membranes of different thicknesses.

The O-rings sit in a recess that allows movement of the O-rings in the radial direction to the inside, so that this the radial movement of the Participate in the membrane by twisting between the membrane and the base.

The membrane and intermediate rings (which are made of metal) are elec tric connected to ground and thus shield the fixed plates from interference fields.

The electronic circuit for recording very small differences in capacitance is shown in drawing 2. Each half of the differential capacitor forms together with the associated circuit part A or B, a monostable multivibrator. Their output signals are fed to the exclusive-or element, and its output only then live if only one of the two inputs is live. The monostable Flip-flops are triggered together and then carry an output signal. As a result the exclusive-or link is the voltage at the output of the exclusive-or element initially zero. Only when the output signal is one of the two monostable multivibrators drops to zero (the flip-flop which just has the smaller capacity) leads the output of the exclusive-or element voltage, and. until they too Voltage of the other jonostabi1en flip-flops drops to zero. At the exit of the exclusive-or link a signal is created, its duration of the absolute capacities Completely independent-1st-ucrein a direct measure for the capacity difference and thus for represents the pressure.

It is now important for the resolution and the accuracy of the device the temporal stability of the output signals of the monostable multivibrator, i.e. if the capacity is not changed, the duration of the output signals should change due to temperature changes, etc. change as little as possible.

This stability depends on the quality of the monostable multivibrator. With flip-flops in the form of integrated circuits, very good Achieve results, however, by building the flip-flops from individual components can be significantly improved. Drawing 3 shows such a structure. He contains constant current sources instead of the resistor in the RC element of the monostable Flip-flop (resistance or constant current sources charge the capacitor with each Measuring cycle), a precision comparator (it compares the voltage on the capacitor with the voltage reference and provides an output signal that is one as long as the voltage on the capacitor is as high as the reference voltage and that becomes zero, as soon as the voltage on the capacitor exceeds this value), and a precision voltage reference. The output signal of the comparator controls a bistable multivibrator, which generates the output signal supplies and discharges the capacitor again; after the output has decreased to zero is. The bistable multivibrator is switched over again by the next trigger pulse.

Triggering can be triggered by a signal derived from the counting pulse take place with a fixed frequency, but can also be used to economize the measurement take place that the trigger pulse from the (at the time of the discharge of the capacitors) delayed output signal of the monostable multivibrator with the longer output signal is formed, which has the advantage that the measurement is independent of the duration of the output signals of the monostable input stage room with the ma.iinal mjgli.chen Frequency takes place. A special starter switch then ensures the safe start-up the processes and (lem switching on.

With the simpler version of the process without compensation of the membrane Steering controls the exclusive-or-member output signal a counter that during the duration of these signals counts pulses from a generator with a constant frequency. At the end of the measuring period, i.e. when the output signal of the monostable multivibrator with the larger capacity has gone to zero, the counting result will be on one Memory given and the counter set to zero after the previous result has been deleted from memory. The memory contents appear on the one hand on a digital one Display and can be fed to a digital / analog converter on the other hand, the enables the display of the pressure curve on a recorder or an oscilloscope. The digital signal can also be further processed directly with a data processing system will.

An evaluation logic determines from the lengths of the output signals monostable tilting stage to which side the membrane is bent straight and thus the (switchable) sign for the display. This sign signal is used also for switching the output signal of the D / A converter at the zero crossing of the pressure when the pressure changes from overpressure to underpressure or vice versa.

This version of the device is also suitable for digital conversion of sound waves in a digital signal The membrane has to be so thin in this case be that it contains the necessary sensitivity and the necessary vibration behavior and the cycle frequency must be so high that high frequencies are still sufficient to be resolved. In connection with further digital processing it receives you have such a noise-free recording method for sound, which is suitable for both the Consumer electronics as well as for measuring purposes.eiguats-The control of the electromagnets in the compensation of the diaphragm from steering is achieved according to the invention by that the digital principle is applied to these electromagnets.

Such an electromagnet is located on both sides of the membrane. This is made up of partial coils whose magnetic field strengths are in one behave in a certain ratio (e.g. l: 2: 4: 8: l6: 32 etc.) and that of (adjustable) Konr; iianf.-Stromquellen be fed, so that durdhKoli, atr he coils set any integer value within a certain range (e.g. 8192 values with 13 sub-coils).

The constant current sources (which are also replaced by other switching elements can be) are from the outputs of two up / down counters (via memory) controlled, which in turn is controlled by the output signal of the exclusive-or element will. The counters are also available with a constant frequency oscillator, the supplies the counting pulses, and with the output signal of the sign logic in connection. The signal at the outputs of the counter or memory also controls the electromagnet in connection with the output signal of the sign logic also the digital display and / or the D / A converter. The memory takes over the current one at the end of the measuring period Counter reading, whereby only the memory (before the transfer) is set to zero (drawing 4).

The function in detail is as follows: Suppose the membrane if in their rest position and none of the partial magnets are switched on, then there is no output signal of the exclusive-or element is generated, the display is zero and the magnets remain inoperative. A change in pressure should now deflect the membrane to one side will. There is now an output signal from the exclusive-or element, which depends on Direction of deflection one or the other counter for counting the pulses of the Generators (upwards) releases. At the end of the measurement period, the result is transferred to the Transfer memory, and the respective electromagnet is controlled so that he the Deflection just Rcompensated, at the same time the counting result appears with the correct sign on the display. The output signal of the sign logic decides which of the Counter is released.

There are now three options for the next measuring cycle: 1.> the pressure hasn't changed. Because of the zero position of the membrane, there is no Output signal of the exclusive-or element and the counter reading and the force of the electromagnet does not change.

2.) the pressure has increased further. An exit signal is generated again of the exclusive-OR element with the same sign as in the first measuring cycle.

The counter continues to count upwards, but not deleted (not deleted ) Counter reading, whereby at the end of the measuring cycle the reading of the digital display and increase the force of the electromagnet.

3G> the pressure has decreased again. It arises again Output signal of the exclusive-or element, but this time with the opposite sign. This controls the counter so that it now counts down. Reduce accordingly at the end of the measuring period the status of the digital display and the strength of the magnet.

If one of the counters comes to zero while counting down, it takes care a switching logic for the fact that the other counter now counts upwards if that The output signal of the exclusive OR element still lasts, so that now the other Electromagnet is put into action. This arrangement avoids that where electromagnets are effective.

The memory can also be absent and the counters can have the electromagnets or control the display directly. The compensation ensures that the membranes are only minimally deflected because the pressure changes compared to the cycle time (e.g. 104 Hz) are slow. The differential capacitor can be chosen so that its sensitivity is very high and its measuring range is very small, since it only still serves as a zero indicator. The volume of the measuring space remains constant, non-linearities and hysteresis phenomena of the membrane play practically no role.

The required shock resistance is achieved on the one hand by the elQastic Suspension of the membrane and its unusual thickness achieved, on the other hand, provides a special suspension of the entire pressure sensor so that the membrane through the shaking movement taking place in a horizontal plane only in the radial direction is moved and there is no acceleration in the axial direction.

The suspension is carried out by a pivotable one around a horizontal axis Elbow, which is also adjustable in height.

The relatively good temperature stability is achieved in that the two monostable multivibrators, which are the only temperature-sensitive components of the circuit (excluding the constant current sources of the electromagnets) double are present and mutually rompens' y çren, so that only a very small Temperature sensitivity remains due to the somewhat scattering properties of the (thermally coupled) monstable flip-flop. According to the state of Technique, these spreads can be kept within very narrow limits.

Temperature-related tension in the membrane can, as already largely avoided due to the elastic suspension.

The digital output signal can easily be used with data processing systems are further processed. This is especially true for the application of the so-called "Warburg's two-vessel method". At the same time, the pressure curve in 2 vessels with identical sample material measured, whereby the two vessels differentiate in just one parameter (e.g. different ratio of liquid to gas room). Through a complicated (previously manual evaluation procedure thereby simultaneously changing the concentration of two different gases (e.g. Oxygen and carbon dioxide).

This evaluation can now be carried out directly and during the measurement by a (fast) data processing system are taken over, and it is thus possible the change in the concentration of two gases, for example in physiological processes such as breathing or photosynthesis, to be recorded continuously and, for example, on a two-channel recorder to represent in diagram form - a task that according to the previous state of the art was unsolvable.

Due to the dependence of the capacitance on the dielectric constant of the medium can be according to claim 8.

also due to differences in the dielectric properties of media the high sensitivity of the evaluation circuit. For this purpose, the Membrane designed as a third solid plate and the medium to be measured between brought the plates. One of the two spaces between the plates can be a Contain reference medium, while the other room takes the medium to be measured. the Spaces can also be designed to be gaseous or liquid media flow through the rooms. A medium can also za-.

next the one room, depending on a modification, for example a chemical one Reaction, flow through the other room, and so the extent of the modification is measured will.

The arrangement described can also be used for diaphragm-free measurement of the Vacuum pressure can be used by connecting one of the two rooms to the vacuum and the other a reference vacuum or a reference gas (e.g. below Normal pressure). The measurement is based on the fact that with increasing Vacuum the dielectric constant approaches that of the vacuum more and more.

The embodiment of drawing l shows a number of for the "Warburg manometry" important details: About the influences of different dielectric constants to be switched off (humidity) are the spaces between the plates of the measuring rooms separated by thin, easily movable auxiliary membranes. In the spaces between the Plates can be atmospheric air, but also a special medium.

Further important details are the connecting pieces, the taps and the Pressure wave throttles. The connecting pieces have the shape of a standard joint 14.5, because the numerous special vessels in use for the "Warburg manometry" have this standard connection and can therefore continue to be used with this apparatus can.

The "pressure wave throttles" are useful because when shaken The sloshing of the liquid creates local pressure waves that affect the membrane set in vibrations These pressure waves are caused by the adjustable "pressure wave throttles", with which a narrowing of the lumen of the connecting pieces is possible from the membrane largely kept away.

The taps are important on the one hand because when connecting the vessels a Overpressure arises. Firstly, this is due to the fact that the connections are greased and so when connecting the connections there is a reduction in volume, secondly in that the vessels are placed in the thermostat after connection and now experience a temperature change.

This excess pressure is avoided by opening the cocks.

In addition, the possibility must exist shortly before the measurement; by zvit the connected vessels with a gas flow (e.g. nitrogen). To this end some of the special vessels are also equipped with a closable opening.

The pressure sensor is designed so that both spaces of the differential condenser can connect with one vessel each.

This enables the system to be used as a differential manometer.

Temperature changes in the measuring vessel play a significant role in manometry Role because, according to the well-known gas laws, the pressure also depends on the temperature. Although the vessels are thermostatted, it is not possible to adjust the temperature to be kept sufficiently constant (it should be constant at 10 2 <10-3 degrees Celsius being held). Changes in atmospheric pressure (weather changes) also have a disruptive influence on the measurement result. To compensate for these disturbances one usually uses a so-called "thermobarometer". This is with one Vessel connected> that is identical with the measuring vessel or with the measuring vessels with the difference that it does not contain the sample to be examined and the pressure change in this vessel the extent of temperature and atmospheric pressure changes reflects.

With manual manometry, the values of the measuring manometer are converted corrected the value of this "thermobarometer".

In the known differential manometry, which deals with special Can carry out capillary pressure, these corrections are made automatically because the thermobarometer vessel on one leg, the measuring vessel on the other leg of the Manometer is connected and pressure changes that occur in both vessels equally run without affecting the height of the liquid limbs.

The system according to drawing 1 can also be used to measure against the Atmospheric pressure can be used; for this purpose the measuring vessel is attached to the lower one Connection piece connected and the upper connection piece folded upwards by 180 ° it is not immersed in the thermostat fluid. The distance between the two connectors each other can be varied by turning the lower part, so that all known Special (Jefct esse can be used.

The dimensions of the system and the type of suspension of the pressure filter are chosen so that si <: h the plant in connection with the numerous more or less in use allows the use of "Warburg apparatus".

According to claim 7.7, the connectors can with a device be provided (such as a suitable hole), the inclusion of a light guide allowed (which is introduced into the bore via a seal, for example), so that the Measurement object can be exposed to cold light from above and inside.

The exposure is important when used in plant physiology, where the behavior of plants and parts of plants are measured when exposed to light target.

In the previous systems, the exposure was from un-.

th over lightbulbs, with the container for the thermostat fluid was made of transparent material and the lightbulbs were placed underneath the container was. This had the disadvantage that on exposure due to the considerable heat development of the lightbulbs a heating of the vessels that cannot be compensated by the thermostat occurred that by the light absorption of the container and Thermostatflüsr fluid a weakening of the light took place and that it was not possible with light one to expose a certain wavelength or a certain spectral range -a Requirement that modern scientific measurements cannot do without can.

With the help of the light guide, the samples can be read without increasing the temperature and exposed directly to light of any wavelength without any weakening of the light.

Claims (11)

Claims 1. Method for capacitive detection - the change in position an electrically conductive plate - or the change in the dielectric constant of media - especially for pressure measurement by means of membranes - with and without digital electromagnetic Compensation of the membrane deflection and system for carrying out the process - particularly suitable for the so-called 'gWarburg manometry' where a metal or metallized plate with two fixed plates a differential capacitor can form characterized in that - the two partial capacitances of the differential capacitor Components are each of a monostable flip-flop and the two flip-flops after a common trigger signal each form a signal, the duration of which depends on the size the respective partial capacity depends and these two signals an exclusive-OR element or a comparable device, so that at the output of the exclusive-OR element a signal is produced, the size of which is the difference in capacitance between the two partial capacities - a periodically occurring trigger signal corresponds to a new Hle'.cycle einleiten.kann, wc-bei this trigger signal starts the monostable multivibrator and the output signal of the exclusive-or element of another digital one or analog processing - that the trigger signal from the delayed signal of the exclusive-or element or the longer one the two output signals of the monostable multivibrators or from the signal of one Signal generator with a fixed frequency can be obtained - the output signal of the Exclusive-OR element can control a counter so that it lasts for the duration of the signal pulses from a signal generator with a fixed frequency counts the result can be transferred to a memory, a display unit and / or a digital / analog converter communicates with the counter or the memory and at the end of each measuring period the memory is set to zero, the memory takes over the result of the counter and then the counter is set to zero - and an evaluation circuit from the blue the output signals of the monostable multivibrator can determine to which side the movable plate is just deflected and thus the sign of the display and / or controls the polarity of the output voltage of the digital / analog converter. 2. The method of claim 1. characterized in that the movable plate is under the Influence of two electromagnets located on either side of the plate these electromagnets are made up of a certain number of sub-coils, can have the same or different numbers of turns - and these sub-coils switched on or off via a control logic can be switched off - the output signal of the exclusive OR element two so-called up-down counter controls so that these during the period of the Signal count pulses from a generator with a fixed frequency, in such a way that at positive Pressure of one meter, with negative pressure the other Counter is in operation and that when the pressure increases the deflection of the diaphragm has, the respective counter increases when the deflection of the membrane decreases has, the counter counts down - whereby the outputs of the counters directly or via memory control electronic switches that switch the partial coils of the electromagnets on or off. switch off and at the same time on a display unit and / or a digital / analog converter - a special evaluation circuit based on the length of the output pulses the monostable flip-flop determines which side the movable plate is on is bent and this decides whether the counter should count up or down - and that another evaluation circuit ensures that if one of the counters has reached zero when counting down and the signal of the Exclusive-Odert Element still lasts, the other counter now up to the end of the signal counts and is in operation until it comes to zero when counting down and the counters are switched over again, 3 Annex for the implementation of the Method according to Claim 1, characterized in that - on a body A a fixed plate A 'is located, another body B is equipped with a fixed plate B' and the movable plate lies between the two bodies via intermediate pieces, so that two spaces and ß arise - the two spaces d and 3 via tubular elements are connected with two connecting pieces. 4. Plant for carrying out the method according to claim 2. according to the system according to claim 3, characterized in that that - the two bodies A and B each receive an electromagnet. 5. The method according to claim 1 and 2, characterized in that - the periodic charging of the capacitor as a time-determining component of the monostable multivibrator can be done via a constant current source - the monostable Tilting stages can consist of several assemblies - essential components of the monostable multivibrators precision comparators and precision voltage sources can. 6. The method according to claim 2, characterized in that - the partial columns the electromagnet can be sneed from adjustable constant current sources, which are switched on or off via the control logic - currents and number of turns the sub-coils can be chosen so that the magnetic field strengths in a certain ratio (e.g. 1: 2: 4: 8: 16 ...) - the outputs of the two Counters or memories can be connected via OR elements and these OR elements control the display or the digital / analog converter. 7. Plant according to claims 3 and 4, characterized in that - the moving plate can be clamped between two O-rings - these O-rings can lie in corresponding depressions of the body A and B - these depressions a clearance of the O-ring to the axis of the two bodies A and B can allow - With a defined distance between the movable plate and the two fixed ones Plates is guaranteed by spacer rings. - these I) istaflzringe easily exchanged for others with a different strength - the spacer rings can be supplemented with spacers of various thicknesses can be - the tipping stages with the directly associated components can be built directly into bodies A and B or into one of the two - the Connection piece can be designed as a so-called standard ground joint NS 14.5 - between the trees d and ß and the Normsohliffstutzen an easily movable gas-tight membrane can lie in the tubular elements can be devices that allow to narrow the lumen - the bodies A and B with suitable elements be clamped together and the whole device via an elbow and a rod-shaped element can be suspended so that - the device in the tripod suspension the so-called Warburg apparatus from Braun, Belsungens can - the device from the bodies A and B both in their height compared to the "Warburg apparatus" can be adjusted as well as about a horizontal axis in the direction of the elbow can be pivoted - the device from the bodies A and B is chosen in its dimensions so that it fits into the "Warburg apparatus - both tubular elements can be provided with a device that allows a closable connection of the lumen with the outside atmosphere or one with the device connected hose - the device easily can be disassembled, so that in particular the movable plate and the spacers can be easily exchanged - the tubular elements with a light guide or a connection for a light guide or a comparable lighting element can be provided, which allows the located in the connected measuring vessel To illuminate samples from above and inside - the connecting pieces point downwards can - the connecting pieces can be adjustable in distance from one another - the fixed plates can be designed so that they simultaneously hold the iron cores represent the two electromagnets 8. The method according to claim 1. characterized in that - the two fixed plates with a third fixed plate form a differential capacitor with a fixed plate spacing - Gases, liquids, vapors or solids in the spaces between the panels are introduced whose dielectric constant has an influence on the capacitance the partial capacitors have - with one room a medium as a reference substance, the other room can contain the medium to be measured - the media flows through the rooms - a medium only through the one, because after a modification through the other room flows and the extent of the change in the partial capacities Modification is measured. 9. The method according to claim 1, characterized in that the movable Plate by forces of a mechanical nature, electromagn. Kind, electrostat. Kind of moves will. 10. The method according to claims 1 and 2 and systems according to claim 3. and 4., characterized in that - they are used for temperature measurement by the Temperature changes the pressure of the medium inside measuring vessels - whereby a The vessel should be exposed to a reference temperature and the other to the measuring temperature can - and the vessels can contain a liquid with high vapor pressure. 11. The method according to claim 1, characterized in that - the movable plate in thickness and type is such that it is sound waves can be moved - the signal of the exclusive-or element in connection with the Evaluation circuit for the direction of movement of the movable plate is a digital one Shows the signal for the sound waves, which includes their amplitude and frequency.