UA57436A - Single-channel meter for measuring parameters of differential transducers - Google Patents

Abstract

The proposed single-channel meter for measuring parameters of differential capacitive transducers contains two active oscillators, a service chamber for installing the transducer, compensation chamber with reference working medium, switching units, a pulse forming unit, a reversible counter, a nonreversible counter, a memory unit, a decoder, a digital indicator, and a control unit.

Description

Description of the invention

The invention relates to means of measuring the electrical parameters of high-frequency differential 2 sensors and can be used to measure the dielectric, magnetic or conductive properties of materials and substances by the value of the electrical impedance introduced into the sensor.

Differential sensors operating in the circuits of high-frequency generators convert the difference between the measured value and the sample value into an increase in AC capacity, LI inductance, or AC resistance of the sensor's electrical circuit. Structurally, the differential sensor has two sensitive elements: the working element, which interacts with the material under study, and the compensation element, which interacts with the sample or reference material. Digital meters of increments of AC, A, AK parameters are most simply implemented using intermediate frequency conversion. To convert the increment of the sensor parameters (AS, AG, AK) into the frequency or period of high-frequency oscillations, autogenerators with IC or ks timing chain are usually used. Alternating periodic connection of the working and compensating elements to the timer circuit of the autogenerator using an automatic commutator makes it possible to extract a low-frequency modulating signal proportional to the difference parameter of the differential sensor from the frequency-modulated high-frequency oscillations of the autogenerator.

A well-known single-channel meter of the parameters of differential sensors (Author's certificate of the USSR

Mo6b55990, cl. (з01кК27/26, 1976), which contains a high-frequency autogenerator, a differential sensor, an automatic switch, the movable contact of which is connected to the timing circuit of the high-frequency autogenerator, and two fixed contacts are connected to the first terminals of the working and compensating elements of the sensor, respectively, the second terminals of which are connected to the body of the meter, a frequency detector, the input of which is connected to the output of a high-frequency autogenerator, a selective low-frequency amplifier, an interrupter, a synchronous detector and an indicator, and a switching generator, the output of which is connected to the reference input of the synchronous detector, with the control circuit of the automatic commutator and through the frequency divider and the single-vibrator with the control circuit of the breaker.

Due to random changes in the frequency of the autogenerator, as well as the nonlinearity of the characteristic of the frequency detector and the unevenness of its frequency characteristic, a large parasitic frequency modulation appears, which does not allow us to distinguish informative changes in the frequency of the autogenerator against the background of random changes.

A known single-channel meter of parameters of differential sensors (US Patent Mo4045728, cl. 3244-59, "0 1977), which contains two autogenerators, a differential inductive sensor, a single-channel measuring "path, which consists of a series-connected frequency converter, the inputs of which connected to the outputs of two autogenerators, a low-frequency amplifier, a synchronous detector and an indicator, as well as a switch, the movable contact of which is connected to the timing circuit of one of the autogenerators, and two fixed contacts - to the first outputs of the working and compensating elements of the differential sensor, the second outputs of which are connected to the common point of the differential sensor, and the switching generator, the output of which is connected to the reference input of the synchronous detector and to the commutator control circuit.

Changes in the frequency of autogenerators due to correlation disturbances are mutually compensated in the frequency "20 converter, which forms a low-frequency signal of the difference frequency. But the commutation disturbances that appear with periodic switching of the commutator in the circuit of only one autogenerator are not compensated and saturate the measuring path, which reduces the accuracy of the measurement. :z" A single-channel parameter gauge of differential sensors is also known (Y.A. Skrypnyk

Switching digital measuring device!. M., "Znergiya", 1973, P.23-25), containing the first and second autogenerators, a capacitive differential sensor with a working chamber filled with the material under investigation and a compensating chamber with a reference material, a commutator, the first and second the inputs of which are connected to the first outputs of the cameras of the capacitive differential sensor, the common output of which is connected to the common ground point of the autogenerator, the output of the commutator is connected to the timing circuit of the first autogenerator, the pulse shaper, the input of which is connected to the output of the first autogenerator , a reversible pulse counter, the counting input of which is connected to the output of the pulse generator, a digital i95) memory element, the address inputs of which are connected to the code outputs of the reversible pulse counter,

Ф a decoder connected to the data bus of the digital memory element, a digital indicator connected to the decoder, a control unit, the outputs of which are connected to the corresponding control inputs of the switch, the reversible pulse counter, the digital memory element and the decoder.

In addition, the single-channel meter contains a signal mixer, the inputs of which are connected to the outputs of autogenerators, a low-pass filter, the input of which is connected to the output of the mixer, and its output is connected to the » input of the pulse generator, as well as a clock pulse generator, with connected to the input of the control unit.

The presence of a digital memory in a single-channel differential sensor parameters meter allows you to reduce the switching frequency to fractions of Hz, which significantly reduces the level of switching interference. Additional gating of the reversing pulse counter at the moment of switching of the sensor chambers allows to almost completely exclude the influence of transient processes in the commutating autogenerator, which increases the sensitivity to small changes in the parameters of the working chamber of the differential sensor.

But the dependence of the result of the measurement of the differential frequency on the temperature and time instability of the parameters of the microcircuits of autogenerators, the timing chain with the cameras of the differential sensor and the power source b5 leads to the fact that with the same relative change of the informative parameter of the differential sensor (AS/C, AIH/// , or dDE/K) the result of the measurement is different, which does not ensure high accuracy of measurement of such relative parameters as dielectric and magnetic permeability or specific electrical conductivity of various materials.

The basis of the invention is the task of creating such a single-channel meter of the parameters of differential sensors, in which the introduction of new elements and connections would make it possible to increase the accuracy of assessing the quality of various materials and substances.

The task is solved by the fact that in a single-channel differential sensor parameters meter, which contains the first and second autogenerators, a capacitive differential sensor with a working chamber filled with the material under investigation and a compensation chamber with a reference material, a switch, the first and second /o inputs of which connected to the first outputs of the cameras of the capacitive differential sensor, the common output of which is connected to the common ground point of the autogenerator, the output of the switch is connected to the timing circuit of the first autogenerator, the pulse shaper, the input of which is connected to the output of the first autogenerator, the reversible pulse counter , the counter input of which is connected to the output of the pulse generator, a digital memory element, the address inputs of which are connected to the code outputs of the reversible 7/5 pulse counter, a decoder connected to the data buses of the digital memory element, a digital indicator , connected to the decoder, the control unit, the outputs of which are connected to the corresponding ones the control inputs of the switch, the reversible pulse counter, the digital memory element and the decoder, according to the invention, a non-reversible pulse counter, the second and third pulse shapers, the second and third switches, while the inputs of the second switch are connected to the opposite inputs of the first switch, the output of the second The commutator is connected to the timing circuit of the second autogenerator, the inputs of the third commutator are connected to the outputs of the first and second autogenerators, the output of the third commutator is connected through the second pulse shaper to the counting input of the non-reversible pulse counter, the output of which is connected through the third pulse shaper to the input of the control unit, one of the outputs of which is connected to the control input of the non-reversible pulse counter, the control inputs of the second and third commutators are connected to the control input of the first Commutator.

Introduction to the scheme of a single-channel meter of the parameters of the differential sensors of the non-reversible pulse counter, two additional switches, two additional pulse shapers, the inclusion of the second switch in the timing chain of the second autogenerator, the connection of the input of the control unit to the outputs of the two autogenerators through the third switch, the inclusion of the non-reversible pulse counter through additional ( The use of pulse generators provided the measurement result in the form of a relative change in the frequency of the autogenerator, and therefore a relative increase in the informative parameter of the differential sensor, and made it possible to exclude the influence of temperature and time changes in the parameters and modes of operation of the autogenerator on the measurement result of relative "g changes in the informative parameters of the differential of the sensor, as well as to reduce the influence of transient processes and switching disturbances on the measurement result, which ensured an increase in the accuracy of the measurement of the dielectric, magnetic, and conductive properties of the controlled medium etc. and materials. yu

The figure (see fig.) shows the functional scheme of a single-channel meter of the parameters of differential sensors.

The single-channel differential sensor parameters meter includes a capacitive differential sensor 1 with a working chamber 2 and a compensation chamber 3, the first, second and third switches - respectively 4,516, " the first and second autogenerators 7 and 8, the first pulse shaper 9, the second and third pulse shapers 10 p») c and 11, non-reversible pulse counter 12, reversible pulse counter 13, digital memory element 14, . decoder 15, digital indicator 16 and control unit 17. and? Capacitive working chamber 2 with the test material and capacitive compensation chamber 3 with the reference material of the differential sensor 1 through the first and second switches 4 and 5 are connected to the timing circuits of the first and second autogenerators 7 and 8, the outputs of which are through the third switch 6 and the second pulse generator 10 are connected to the non-reversible pulse counter 12. The output of the non-reversible pulse counter 12 through the third pulse shaper 11 is connected to the input of the control unit 17. To the output of the first

Ш- autogenerator 7 directly through the first pulse shaper 9 is connected the reversible counter of their pulses 13, to the code outputs of which a digital indicator 16 is connected through the digital memory element 14 and the decoder 15. The first output of the control unit 17 is connected to the control inputs of the switches 4, 5 and 6, about the second and third outputs - to the non-reversible pulse counter 12 (zeroing, counting), fourth, fifth,

Ф sixth output - to the reversible pulse counter 13 (resetting, counting and reversing), the seventh output - to the digital memory element 14, the eighth output - to the decoder 15.

A single-channel differential sensor parameter meter works as follows.

The working chamber 2 and the compensating chamber Z of the capacitive differential sensor 1 are structurally chosen to be the same, which ensures the equality of their capacitances С.-Со in the absence of contact of the sensor electrodes with

P" with the test and reference material or when both chambers of the sensor are filled with the same substance. When working chamber 2 is in contact with the material under investigation and air is used as a reference material, the capacity of the working chamber can be represented as follows: 60

ShtsSa A, (0 where АС-СоО(Е-1) is the increase in sensor capacity due to contact with the controlled material; Е is the dielectric permeability of the material being tested. 65 With the help of switches 4 and 5, chambers 2 and Z of the capacitive differential sensor 1 are connected alternately to timing circuits of autogenerators 7 and 8. At the same time, the switches and digital elements of the meter circuit are controlled from eight outputs of the control unit 17, to the input of which clock pulses are received from the pulse generator 11. With the arrival of the first clock pulse signal from the first output of the control unit 17, switches 4, 5 and 6 are set to the initial position shown in the figure, and the non-reversible pulse counter 12 and the reversible pulse counter 13 are reset to zero by signals from the second and fourth outputs of the control unit 17. At the same time, the capacity of the compensating chamber З - Со is included in the timing circuit of the autogenerator 7, and in timing circuit of the autogenerator 8 - capacity of the working chamber 2 - Su. Frequency generated the oscillations of the autogenerator 8 with the CS timing circuit is determined by the expression: -MV(Ссо), (2 70 х-КК(СкСо), (2) where K is the proportionality coefficient, which depends on the parameters of the autogenerator microcircuit and the value of the supply voltage;

K; C is the constant resistance and capacity of the timer circuit of the autogenerator. /5 The frequency of generated oscillations of autogenerator 7 made according to the same scheme:

Ro-K/K(SkSo) (3)

When the electrodes of the working chamber 2 of the differential sensor 1 come into contact with the material under study, the oscillations of the autogenerators become different (5-19) and alternate in turn at the output of each of the autogenerators depending on the position of the switches. Shapers 9 and 10 form short pulses from the oscillations of autogenerators 7 and 8, which are fed to the counting inputs of the non-reversible pulse counter 12 and the reversible pulse counter 13. At the specified position of the switches, pulses following with frequency b are fed to the input of the non-reversible counter 12, and to the input reversible counter 13 - pulses with a frequency of The non-reversible counter 12 accumulates pulses until it is completely filled. The filling time is determined by formula 29: "

Meme, (4) . Я Я я - g zo de Mo - the total number of pulses at n digits of the counter. For the time being, the reversible counter 13 is closed for counter pulses (counter gating mode). (ze)

At the moment of filling the non-reversible counter 12 with the pulse generator 11, a short pulse is formed due to the voltage drop at the output of the counter, which, as a clock pulse, enters the input of the control unit 17. With the arrival of the second clock pulse according to the signal of the control unit 17 from the fifth output to the reversible pulse counter - 13 receives the "count" command and the reversible pulse counter 13 begins to count and accumulate pulses in the mode of their addition. At the same time, the non-reversible pulse counter 12 begins to fill up again and after the end of time l-ldLi issues another clock pulse with the help of the pulse generator 11. With the arrival of the third clock pulse, the counting of pulses in the reversible pulse counter 13 ends, in which the number of pulses has accumulated: « - s Mi aa Maya (5) iv . . and?" From the first output of the control unit 17 comes the command to switch switches 4, 5 and b, and to the reversible pulse counter 13 from the sixth output - the "reverse" command. In the opposite position

Commutators in the autogenerator 7 begin to generate oscillations with a frequency y, and in the autogenerator 8 - s oscillations with a frequency Я. At the same time, the input of the non-reversible pulse counter 12 and the reversible pulse counter 13 begins to receive pulses that follow only with a frequency of

Ш- In the non-reversible pulse counter 12, another accumulation of pulses is carried out until it is completely filled for a time equal to the previous interval: (95) climbed (6) 4) о, и и - .

During dz, transient processes in autogenerators 7 and 8, caused by the switching of capacitors Srii C, in the timing circuits of these autogenerators are attenuated and commutation disturbances disappear. During this time interval, pulses are not counted in the reversible pulse counter 13 (counter gating mode). When the non-reversible pulse counter 12 is filled, a fourth clock pulse is formed, which enters the input of the control unit 17. At the output of the control unit 17, the "count" command is formed again, which is fed to the control input of the reversible pulse counter 13.

During AC-LC time and in the reversible pulse counter 13, the number of pulses is subtracted from the accumulated pulses:

Ma to her and Mo (7

The remaining pulses in the reversible pulse counter 13 until this moment will be: b5

I (8)

With the arrival of the fifth clock pulse from the non-reversible pulse counter 12 on the signal of the control unit 17, the counting of pulses stops, and switches 4, 5 and b return to their initial position. The input of the reversible pulse counter 13 again receives pulses with a frequency of Х), and the input of the non-reversible pulse counter 12 continues to receive pulses only with a frequency of Х.

Upon filling the non-reversible pulse counter 12, the sixth clock pulse is produced after a time interval of lif5-li. According to the command from the seventh output of the control unit 17, a parallel binary code proportional to the number of remaining pulses (8) is fed from the code outputs of the reversible pulse counter 70 to the address inputs of the digital memory element 14.

By the end of this interval, transient processes in autogenerators and switching disturbances in the sequence of counting pulses end. With the arrival of the seventh clock pulse through the time interval of the holes at the command of the control unit 17 in the reversible pulse counter 13, a new counting of pulses begins with obtaining the result according to expression (5). At this time, the data buses of the digital memory element 14 are connected to the digital indicator 16, where the measurement result is displayed, on the command from /5 of the Eighth output of the control unit 17 to the decoder 15. This completes the measurement cycle.

From the moment of the arrival of the fifth clock pulse, a new measurement cycle actually begins with the gating mode of the reversible pulse counter 13, which continues during the next seven clock pulses. At the same time, the result of the previous cycle is indicated on the digital indicator 16.

The pulse residual code (8) taking into account the frequency values (2) and (3) has the form:

Ma - M - Ou - MS, So Sv) (8) -MASspSyus).

It can be seen from relation (9) that the measurement result is proportional to the relative change in the capacity of the working chamber 2 of the differential sensor 1.

Since changes in the capacity of the working chamber 2 of the differential sensor 1 relative to the air medium of the compensating chamber Z of the differential sensor 1 is determined by the dielectric permeability of the material under investigation, the indicated code: Ge) and MU Moss Ks sah (0) and. "

In the case when the capacity of the empty chamber of the differential sensor is greater than the capacity of the capacitor of the timer circuit of the autogenerator (Co»C), we have: -

IC c)

Ma (EM, (t i.e., the measurement result is proportional to the dielectric permeability. "

As can be seen from expressions (10) and (11), the digital result of the Mz measurement does not depend on such unstable values as the parameters of autogenerator microcircuits, power sources, resistances of timing circuits. The contents of the memory cells ts for the corresponding codes on the address buses of the digital memory element are filled in the process of setting up the single-channel meter with numbers that characterize the state and properties of the monitored material. This allows us to express the result directly in measured physical quantities, skipping the stage of calculating these quantities based on the values of the dielectric permeability of the material under study.

The considered single-channel meter of the parameters of differential sensors allows to detect changes in the dielectric permeability of solid, liquid and gas media in the third decimal place, which gives the opportunity to control the moisture content of materials or the degree of contamination or their dilution, as well as to record the presence of foreign inclusions (sediment, etc. n.). - Depending on the design of the differential sensor for relative changes (AS/S, DILI, or DE/K), it is possible to measure also small displacements, deformations of elastic elements, parameters of object movement, etc.

Claims (1)

The formula of the invention is a single-channel meter of the parameters of differential sensors, which contains the first and second autogenerators, a capacitive differential sensor with a working chamber filled with the material under investigation and a compensating chamber with a reference material, a switch whose first and second inputs are connected to the first the outputs of the cameras of the capacitive differential sensor, the common output of which is connected to the common ground point of the autogenerators, the output of the commutator is connected to the timing circuit of the first autogenerator, the pulse shaper, the input of which is connected to the output of the first autogenerator, the reversible pulse counter, the counter input of which connected to the output of the pulse shaper, a digital memory element whose address inputs are connected to the code outputs of the reversing pulse counter, a decoder connected to the data buses of the digital memory element, a digital indicator connected to the decoder, the control unit, the outputs of which are connected to the corresponding control inputs of the switches ator, 65 reversible pulse counters, a digital memory element and a decoder, which is distinguished by the fact that a non-reversible pulse counter, second and third pulse shapers, second and third commutators are additionally introduced into it, and the inputs of the second commutator are connected to the opposite inputs of the first switch, the output of the second switch is connected to the timing circuit of the second autogenerator, the inputs of the third switch are connected to the outputs of the first and second autogenerators, the output of the third switch is connected through the second pulse shaper to the counting input of the non-reversible pulse counter, the output of which is through the third pulse shaper connected to the input of the control unit, one of the outputs of which is connected to the control input of the non-reversible pulse counter, the control inputs of the second and third switches are connected to the control input of the first switch. " (Se) (ze) " in I c) - and? 1 -and sh" (95) 4) 60 b5