SU1383226A1 - Parameter indicator for dielectric media and materials - Google Patents

Abstract

The invention can be used to analyze the physicomechanical properties of non-conducting or weakly conducting media, for example, lightly saline soils, as well as for technological control of production processes for a number of materials and products. The meter of parameters of media and materials contains a measuring generator 5. with a master circuit, switching generator 1, automatic switch 11, measuring 13 and exemplary 14 capacitors, reversible counter 7, building block 6, indicator 8, comparator 12 codes , control unit 15, current source 4, ballast resistive-capacitance chain 3, amplifier 9, switch 2 and varicap 10. Measurement accuracy increases and functionality is expanded by separately measuring active and reactive constituting the complex impedance. 1 il. about s (l

Description

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The invention relates to non-destructive testing of the parameters of substances, materials and products based on dielectrics, and in particular, can be used both for analyzing the physicomechanical properties of non-conductive or weakly conducting media, such as lightly saline soil, and for technological control of production processes materials and products.

The aim of the invention is to improve the measurement accuracy and enhance the functionality by separately measuring the active and reactive components of the impedance.

On the drawing is a block diagram of the meter.

The meter contains switching generator 1-, switch 2, ballast resistive-capacitive chain 3, current source 4, measuring generator 5, gating unit 6, reversible counter 7, indicator 8, amplifier 9, varicap 10, automatic switch 11, comparator 12 codes, measuring capacitor 13, model capacitor 14, control unit 15.

The device works as follows.

The control voltage of the switching generator 1, periodically with frequency. switching 5 switches the automatic switch 11, through which the measuring or reference capacitors 13, 14 alternately connect with the same frequency to the driving circuit of the measuring oscillator 5. The measuring capacitor is realized in the form of capacitor plates between which the sample under test is placed. In this case, the frequency of the auto-oscillator 5 varies with the switching frequency I in accordance with the non-identical values of the capacitors 13 and 14. The generator produces a frequency-modulated voltage that goes to the counting input of the reversible counter 7. The input of the counter 7, which controls the reverse, is connected to switching generator 1. Between the output of the generator 5 and the counting input of the counter 7, a pulse gating unit of the measuring generator 6 is switched on, the purpose of which is to exclude

the passage of counted pulses at the moments of switching capacitors 13 and 14 by switch 11. Gating reduces the measurement error of the number of pulses during a switching period of 2/1/57 T, caused by transients of generator 5 and switch 11. Thus, gating unit 6 generates pulses of a certain the duration (more than the constant transient time) in each half period T; (/ 2 switching capacitors 13 and 14.

The measurement of the reactive component of the resistance X from the capacitor 13, which in the presence of the object of study is complex, is carried out using the exemplary capacitor 14 (with low losses). The value of the capacitance changes as a result of the action of the actuator included in the control unit 15. The input of block 15 comes from the output of the code comparator signal, the sign of which depends on the ratio of the codes being compared, at the moment the strobe pulses arrive at the comparator 12 codes. The purpose of the code comparator is to fix the sign and the number of pulses proportional to the frequency difference of the measuring generator 5 during the switching period T |, it is input to device 15. The function of strobe pulses to the comparator is to synchronize the moment of comparison of comparator codes 12. Control unit 13 rebuilds the reference capacitor 14 until the output code of the counter 7 becomes zero - this is in the General case, i.e. when half-periods are symmetric. However, due to the imperfection of the switching circuits, it is necessary to preset the initial value of the comparator 12 codes, which is carried out at the device calibration step before the measurement.

The described step of measuring the reactive component Xc, which characterizes the properties of the measurement object under investigation, placed between the plates of the measuring capacitor 13, does not differ from the known autogenerator methods. It consists in fixing the equality of the frequencies of the measuring generator at the time of mutual replacement of the reference and measuring capacitances.

A feature of this meter is that this stage of compensation is. of the reactive component X (, the complex impedance of the object is not following; this is the stage of initial setting the value Co of the reference capacitor 14. Relative to this value, at the second stage of the measurement, the value of the active connection of the compressing component r is measured. Cf, where C is the final value of the reference capacitance, which it receives upon completion of the second 15 measurement stage.

At the second measurement stage (g. Measurement mode), switch 2 is in the closed state. At the same time, the use in a closed circuit consisting of a series-connected generator 5, a source 4, a switch 2, an amplifier 9, a varicap 10 and a ballast chain 3 (resistor and capacitor in parallel), a source of current 4 supplying the measuring generator 5 allows, at the connection point of the ballast chain, to select the envelope of the switching frequency SI whose amplitude is proportional to jO of the difference in losses in capacitors 13 and 14 included in the measurement generator 5 s with the reference circuit, which is used as the resonator The nsn system contains capacitors 13 and 14 and inductance (not shown). .

From the condition Ij IP + 1c - const, where Ij is the current of source 4, defined by its internal res. Q by glaze;

1 - constant current component, closing with through the resistor: the resistor of the chain 3 and the resonant circuit of the generator 5; .ds IP is variable component,

closing through the capacitor of the chain 3 and the resonant generator 5, it follows that the change in the equivalent resistance of the driver circuit of the generator 5 (resonant circuit with capacitors 13 and 14) causes the redistribution of current Ip and I ;, which changes the voltage drop across the resistor chains 3. This makes it possible to choose the envelope of the switching frequency caused by the inequality of the impedances of the capacitors 13 and 14.

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The selected envelope is used in the mode of measurement of the active component Gy. This envelope is fed through amplifier 9 as a modulating voltage to varicap 10 for additional frequency modulation of oscillator 5.

In the measurement mode of the active component of the impedance, the switch 2 is in the closed position. However, due to the different impedance values of the capacitors 13 and 14 connected by the switch 14, the direct current through the resistor will be modulated with the switching frequency S1. Consequently, the constant voltage across the ballast resistor entering the input of amplifier 9 will vary according to the same law. The purpose of the capacitor of the chain 3 is to filter the high-frequency component of the oscillator 5. A switching frequency voltage proportional to the losses in the medium under study causes frequency modulation of the oscillator 5 due to the periodic variation of the varicap capacitance 10, i.e. The amplitude modulation in the power supply circuit of the generator 5 generates the frequency deviation of the same generator.

This frequency deviation with the switching frequency si must be compensated for by equalizing the impedances of the capacitors 13 and 14, and the indication of the equality of these and ffedanes is controlled by the equality of the frequencies of the generator 5 on the half-periods T c / 2 by the measuring information conversion path used earlier, at the first stage in mode-: measure X. i.e. the indication of the equality of the HNme-data occurs with the help of the reversible counter 7. The output code of the counter, as in the first mode, is information for controlling the capacitor 14 through block 15. The process of regulating the capacitance value will continue until the capacitor 14 will not reach the value C, In this case, the energy consumption from the current source 4 in both clock cycles of the switch 11 will be the same, which will lead to the disappearance of amplitude modulation at the input of the amplifier 9. In this case, the active component count go resistance studied

 OR material may be determined by the ratio

with

one

СС

Where is BOS C to - Cf.

The measurement and calibration process is as follows.

At the first stage, the zero is set, i.e. The initial capacitance values of the measuring and reference capacitors 13 and 14 are typed. To do this, in the absence of the object being measured, the switch 2 is opened and the zero value of the comparator code 12 is set. According to the steady-state value of indicator 8, the calibration process is completed. Next, set the value of the code of the comparator 12 to the value of the readings of the digital indicator 8 taking into account the sign, while after the end of the transients on the indicator 8 will automatically be set to zero. The preset code of the comparator 12 is determined by the asymmetry of the duty cycle of the durations of gated half periods of time intervals corresponding to the switching frequency and depends on the technical performance of the gating unit 6. The calibration of the meter is completed by counting the initial value.

of the object being lined up and its value at the moment of compensation of the amplitude modulation of the switching frequency 5 on the resistor of the chain 3, caused by the active loss g of the measurement object placed between the plates of the reference capacitor 14.

This modulation is reduced by the reactance of the reference capacitor 14. The capacitor 14 is tuned in this mode by the control unit 15. In this case, the above relation is fulfilled, from which it is easy to determine r from the known frequency of the generator 5.

The absolute value of the frequency s in the expression for r ,, can be determined from the indications of indicator 8. For this, the reverse control circuit is turned off and the indicator counts the number of generator pulses 5 for the switching half period T .. The specified mode is embedded in the structure of the switching generator 1.

Formula inventions

A meter of parameters of dielectric media and materials, containing a measuring generator with a time master circuit and a switching generator, an automatic switch.

Csi sample reference capacitor 14 35. measuring and sample condensation on its scale,

The process of measuring the reactive component of the complex impedance of the measurement object consists in determining the scientific research institute of the difference in the values of the reference capacitance between its indications C, counted after the introduction of the measurement object into the capacitor 13, and its value counted in the calibration mode, i.e. ХС 1 / w (C о-С „).

The peculiarity of the measurement mode of the active component g of the proposed device is the possibility of its registration by the compensating reactive component of the reference capacitance when the condition is met.

wCC. - CJ

where (C - C) is the increment of the reference capacitance between its value when the reactive component is counted

tori, reversible counter, gating unit, indicator code comparator and control unit, while the middle contact of the automatic switch is connected to the master circuit of the measuring generator, the output contacts of which are connected to the common bus of the meter through measuring and reference capacitors,

The output of the measuring generator is connected through a serially connected gating unit and a reversible counter is connected to the indicator input, the output of the switching generator is connected

to the control inputs of the automatic switch, gating unit and reversible counter, the outputs of the latter two are connected to an indicator and code comparator, the output of which is connected to an image capacitor through the control unit, characterized in that, in order to improve the accuracy of measurement and expansion

7 13332268

functionality through a resistive-capacitive ballast separate measuring active and re-chain - to the common meter bus and active components of the complex through the switch to the amplification-resistance input, a non-liter is connected to it, the output of which is connected to one current point; the varicap terminals and the medium-capacitive circuit, the amplifier, and the switch off the aBToMaTH iecKoro contact, the mixer, the varicap, with the first switch ,. and another change of the current source is connected to the capacitor, connected to the common bus to the measuring generator, and the second Q meter.

Claims (1)

Measuring media and a measuring supply circuit and a switching generator, an automatic switch, 35 measuring and reference capacitors, a reversible counter, a gating unit, an indicator; a code comparator and a control unit, in this case, the middle contact of the automatic switch is connected to the timing circuit of the measuring 40 generator, the output contacts of which are connected to the common bus of the meter through the measuring and reference capacitors, the output of the measuring generator through a series-connected gating unit and a reversible counter connected to the indicator input, the output of the switching generator is connected to the control inputs of the automatic switch, the gating unit and the reversible counter, the outputs of the last two are connected to an indicator and a code comparator, the output of which through the control unit is connected to an exemplary capacitor, characterized in that, in order to increase the measurement accuracy and expand the functionality by separately measuring the active and reactive components of the complex resistance, a current source is introduced into it , ballast resistive-capacitive chain, amplifier, switch, varicap, while the first output of the current source is connected to the measuring generator, and the second through the ballast resistive-capacitive chain - to the common bus of the meter and through the switch to the input of the amplifier 5, the output of which is connected to one of the terminals of the varicap and to the middle contact of the automatic switch. and the other Varicap pin is connected to a common bus from 10 gauge.