SU1746280A1 - Analyzer - Google Patents

Abstract

Use: dielectric control of liquids and solids in the most diverse areas of industrial production. The invention: in the known device dielectric control, containing a capacitive sensor included in the resonant circuit of the measuring two-pole with a modulating capacitor, specifies the generator. a communication element of a master oscillator with a measuring circuit, a modulator, a demodulator, a phase-sensitive amplifier, a reversing motor, and a compensating capacitor, additionally introduced an analog switch connected between the demodulator and the phase-sensitive amplifier. RS flip-flop, the output of which is connected to the control input of an analog switch, synchronization unit, the input of which is connected to the control input of the analog switch, synchronization unit, the input of which is connected to the output of the modulator and the control input of the modulating capacitor, inverter, four-bit Single binary counter and serially connected clock generator and frequency divider. The output of the latter is connected to the clock-input of the synchronous RS-flip-flop and the counting input of the four-bit binary counter, the output of which is connected directly to the Reset input of the synchronous RS-flip-flop and through the inverter to its input Installation. Inputs The reset of the frequency divider and four-bit binary counter is connected to the output of the synchronization unit (reset pulse shaper). 1 il. VI O y 00 o

Description

The invention relates to a measurement technique and can be used to measure dielectric parameters and control the composition of liquid and solid substances.

A dielectric moisture meter is known, which consists of a generator connected to a measuring two-terminal device made in the form of a resonant circuit containing a capacitive humidity sensor. The resonant frequency shift caused by a change in the humidity of the sample under investigation measures the phase detector, the output of which controls two identical varicopes through a feedback circuit. One of them balances the resonant circuit, the second controls the pulse width of the RC generator, which

characterizes the humidity value and is converted to the output voltage of the moisture meter.

The disadvantages of this device are the strong dependence of the magnitude of the error on the losses in the test material, i.e. there is a variation of the metrological characteristics of the device.

The closest to the technical essence of the invention is a device for measuring the dielectric constant of conductive materials, comprising a measuring two-pole in the form of a resonant circuit with a parallel connection of inductance, a capacitive sensor, a variable capacitance capacitor and a circuit of two counter-connected varicaps, as well as a high-frequency generator, communication element, modulator, demodulator, adder, null-organ containing a phase-sensitive amplifier and reversing motor, mech canonically generator coupled to the compensation axis.

The disadvantage of the device is the presence of an error caused by the conductivity of the test medium and the impossibility of completely eliminating this component.

The aim of the invention is to improve the measurement accuracy.

The drawing shows a block diagram of a dictometric analyzer.

The device contains a high-frequency generator (VCG) 1. a communication element 2, a measuring two-terminal (ID) 3 in the form of a resonant circuit with a parallel connection of inductance coil 4, a capacitive sensor 5, a variable capacitance capacitor b and circuit 7 of two oppositely connected varicaps, average the point of which is connected to the output of the modulator 8. The device also contains a demodulator 9, an analog switch 10, a phase-sensitive amplifier 11, a reversing motor 12, a synchronous RS trigger 13, a synchronization block 14, a generator 15 clock pulses, frequency divider 16, four flip-flops 17-20 four-bit binary counter 21 and inverter 22. Generator 1 output through serially connected communication element 2, ID 3, demodulator 9 and analog switch 10 connected to the input of phase-sensitive amplifier 11. Axis a compensating variable capacitor 6 is mechanically connected to a reversing motor 12. A four-digit binary counter 21 is made as a serial connection of the trigger 17-20, the control input of the analog switch 10 is connected to the output of the blue chronic RS flip-flop 13. The output of the modulator 8 is connected to the input of the synchronization unit 14, the output of which is connected to the parallel inputs Reset triggers

17-20 counter 21, the output of which is connected with the input Reset of the synchronous RS-flip-flop 13 and through the inverter 21 with its input Installation. The clock pulse generator 15 is connected via frequency divider 16 to the synchronizing clock inputs of counter 21 and RS flip-flop 13, and the Reset input of frequency divider 16 is connected to the output of the synchronization unit.

The device works as follows.

ID 3 through the element 2 of the connection with the output of the VCG 1 receives a high-frequency voltage. When changing the capacitance of the sensor 5 (for example, after filling the test

0) the circuit is detuned with respect to the frequency of the RF generator. Due to the inequality of the transmission coefficients of the measuring circuit with two values of the capacitance of modulating varicaps 7

5, the high frequency voltage across the circuit is amplitude modulated. The variation of the capacitance of the varicaps is carried out by rectangular pulses, coming together with the bias voltage from the output

0 of the modulator 8. The modulating pulses are generated by amplifying and limiting the sinusoidal voltage supplying the exciting winding of the reversing motor 12.

5 The low-frequency (modulation frequency) envelope of the RF voltage on the ID 3 is separated by the demodulator 9. The signal from the demodulator 9 is fed through an analog switch 10 that excludes from the signal

0 detuning areas distorted by the transition process to a phase-sensitive amplifier 11 controlling the operation of the reversing engine 12. The engine changes the capacitance of the compensating capacitor 6

5 so that the measurement circuit is balanced and the ID 3 is tuned to resonance.

By changing the capacitance of the compensating capacitor 6, the dielectric constant of the substance filling the sensor, or its composition, is determined.

An analog switch 10 in each half-period passes only part of the signal breaking. Are cut areas

5 adjacent to the front and rear fronts. This operation is carried out by feeding to the control input of the analog switch the corresponding control pulses from the 3-tripper output 13. The control pulses are formed in the following way. At the moment when the polarity of the modulating voltage is changed, the synchronization unit 14 generates short reset pulses, setting the frequency divider 16 and the four-bit binary counter 21 to the zero state. The role of the frequency divider on the number N can be performed by a pulse counter. After the 15 N pulse from the clock output, a primary pulse appears at the input of the frequency divider 16, setting the RS flip-flop 13 to the one state, since the setting at its time is present 1. There is a high voltage level the output of the RS flip-flop opens analog switch 10, allowing the unbalance signal to pass through until eight pulses from the output of the frequency divider are sent to the four-bit binary counter 21. When the eighth pulse arrives, the output of the most significant bit of the counter and the input Reset of the RS flip-flop set to level 1.

By the ninth pulse arriving at the clock input from the output of the 16 frequency divider, the RS flip-flop will be set to the zero state, prohibiting the passage through the 10 switch part of the unbalance signal adjacent to the falling front, considered, for example, of the positive half-period.

When the polarity of the modulating voltage is changed again, the synchronization unit 14 sets the divider 16 and the counter 21 to the zero state and the operation cycle of the analog switch control circuit repeats. Obviously, if the frequency of the clock pulse generator (mt.i) is

, 10 n

Satisfy the ratio of IT and Q r T-,

where Tm is the oscillation period of the modulator, then from the unbalance signal in each half-period, equal length sections will be cut adjacent to the leading and trailing edges and equal to

N

0.05 Tm. (one)

The change in the duration of the cut sections during the operation of the device, due to the onset of the phase shift between the frequencies fT and. and fM, due to inaccurate fulfillment of relation (1) n, exceeds the time equal to the period of 1 / fr clock and.

The duration of the section to be cut adjacent to the leading edge must exceed the time of the transient process that occurs in the circuit when it is modulated

parameters. And the duration of the section to be cut adjacent to the trailing edge should preferably be kept equal to the front section, since this does not cause a phase shift of the first harmonic signal

imbalance with respect to the modulating signal and the harmonic content is reduced. These factors can increase the sensitivity of the auto-tuning system and increase the measurement accuracy.

Claims (1)

DETAILED DESCRIPTION OF THE INVENTION A dielectric analyzer comprising a series-connected high-frequency generator, a communication element, a measuring two-pole and demodulator, as well as a modulator, a phase-sensitive amplifier and a reversing motor, the measuring two-pole having in parallel connected inductance, a capacitive sensor, a variable capacitance capacitor and a circuit of two oppositely connected varicaps, the midpoint of which is connected to the output of the modulator , and the axis of the compensation capacitor is mechanically connected to a reversible motor, characterized in that, in order to improve the measurement accuracy, analogs are introduced into it switch, synchronization unit, generator clock pulses, a frequency divider, a synchronous RS trigger, a four-bit binary counter in the form of four series-connected triggers and an inverter, with an analog switch connected between the demodulator and the phase-sensitive amplifier, and the control input of the switch is connected to the output of the synchronous RS-flip-flop, the output of the modulator is connected to. sync block input, the output of which is connected to the parallel inputs Reset trigger triggers whose output is connected to the input Reset synchronous RS-trigger and through the inverter with its input Installation, clock generator through the frequency divider is connected to the clock inputs of the counter and RS-trigger, and the input Reset frequency divider connected to the output of the sync block.