SU1320541A1 - Method of converting pressure to electric signal - Google Patents

Abstract

The invention relates to electrohydropneumatic control circuit control circuits and allows to increase the noise immunity, sensitivity, accuracy of conversion. To do this, in implementing the invention, the currents in the capacitive under-compensation sensor of the electrodynamic inverse converter and the reference capacitor are statistically balanced, choosing the period for changing the reference voltage with a substantially shorter time constant due to the parasitic capacitances of the communication lines of the capacitors. A feedback signal (output voltage) is simultaneously applied to the input of an electrohydrodynamic inverter with a light dielectric working fluid and a capacitive undercompensation sensor, switching the latter between the output voltage and a part of the reference voltage. 2 Il. sl co w o sd 4

Description

The invention is intended for use in the control circuits of electro-hydraulic and electropneumatic automation systems.

The aim of the invention is to increase the noise immunity, sensitivity and accuracy of the conversion.

FIG. 1 shows an apparatus for carrying out the method; in fig. 2 shows an electrohydrodynamic inverter circuit with a capacitive under-compensation sensor.

The device contains a control unit 1, dividers 2 and 3 of the reference voltage Uo, modulators 4 and 5, lines 6-8 of communication (with parasitic capacitances), reference capacitor 9 (reference capacitance Co), charge amplifier 10, demodulator 11, a discrete integrator 12, an electrohydrodynamic reverse driver 13 and a capacitive undercompensation sensor 14, which are a single structural unit 15 (Fig. 2).

As a nrimer, FIG. 2 shows the scheme, EGNP-1 2 with a single-phase dielectric. In constructive terms, it consists of two needle-type electrodes 16 - tube 17 placed in a dielectric body 18, the space between which is filled with a single-phase dielectric (mineral oil). Capacitive sensors, formed by metal plates 19 and 20, 21 and 22, respectively, with a two-phase dielectric between them, such as an air-working fluid, were used as the undercompensation sensor. In the circuit (FIG. 1), one under-compensation sensor 14 is used, although differential activation is possible.

ten

15

20

25

thirty

ion current

The period of the signals of the transmitter (Fig. 1) is chosen for the dock greater than the parasitic reloading parasitic 6-8.

The increase in noise is due to

The influence of parasitic 7 by the magnitude of C Odr gain of the Tegrator 12 and the expression

WITH

and;

in the circuit of FIG. 1 to d 10, which is possible due to the formation of a capacitance circuit.

Reducing the effects of 6 and 8, connected by Co and Cx, is provided by modulators time 4

Introduction of demodulation conversion to reduce the effect of its characteristic characteristics of the feedback signal of the demodulator 11. When operating at low voltages t / o, the good value of the amplitudes with the bottom coefficient of the device as a whole.

To ensure the direct dependence of Uaax, a significant displacement of

The conversion method is implemented in s by modulator 5.

45

device as follows.

The inlet pressure P is converted to a change in capacitance (C) in undercompensation sensor 14. When pressure is applied (Fig. 2), the level of the dielectric fluid between windings 19 and 20, 21 and 22 changes, 40 the change in capacitance C is converted into alternating current proportional to biased (using dividers 2 and 3) input signal, the resulting AC signal is compared with an AC signal proportional to the reference capacitance of the capacitor 9 (Co) using the splitter 2, modulator 4 and capacitor 9.

The resulting signal difference is amplified in charge amplifier 10 and in discrete integrator 12, before which the signal is demodulated. The feedback circuit of amplifier 10 includes windings of sensor 14. The current in the capacitor is created by modulating the modulator 4 with the reference voltage Uo, and the current R of the capacitor C of the sensor 14 with the output voltage OUTV-Electrohydro1I; at-. iiii-KrimH to its electrodes 16 and 17 is sharply non-. ; 1P (native gender creates unipolar P50

55

To do this, the sensor of the torus 5 switches the voltage and voltage, determined by the division factor

Claims (1)

Formula of The method of converting a signal by changing the capacitance of capacitance to a capacitance output signal and converting the signal output to a change in the dynamic dynamic feedback by input of a signal that, for the purpose of sustainability, senses the method, the change in compensation is proportional to the biased signal, the resulting current is compared to the current si, proportional to 0 five 0 five 0 current of ions transmitting the amount of its movement to the environment. The period of the alternating current signals in the circuit (Fig. 1) is chosen to be no less than an order of magnitude greater than the time constant for recharging the parasitic capacitances of communication lines 6-8. The increase in noise immunity of the method is achieved due to the following points. The effect of the parasitic capacitance of the link 7 by the magnitude of C is determined by the value of the gain factor of the amplifier 10 and the integrator 12 and is expressed by the factor WITH and; in the circuit of FIG. 1 k must be at least 10, which is possible due to performing a capacitance-voltage conversion according to an astatic circuit. Reducing the effect of the capacitance of the communication lines 6 and 8 connected to the other terminals Co and Cx is provided by choosing the time constant of the modulators 4 and 5. The introduction of the demodulator 11 into the direct conversion circuit significantly reduces the influence of its parameters on the static characteristics of the device, since the feedback signal is taken already after the demodulator 11. In this case, the amplifier 10 operates at small values of the output voltage t / out whereby the permissible interference amplitude value is determined by the interference suppression ratio of the entire device as a whole. To provide a direct proportional dependence (Pb), an additional voltage offset was introduced on the dates by modulator 5.   modulator 5. For this purpose, the sensor 14 is switched by means of the modulator 5 between the output voltage and the part of the reference voltage, determined by the product m. Of the division factor of the dividers 2 and 3. Invention Formula A method of converting pressure into an electrical signal by converting pressure into a capacitance change in a capacitor undercompensation sensor, into an electrical output signal, followed by an inverse conversion of the electrical output signal into a pressure change and electro-hydrodynamic balancing on the input pressure feedback circuit with an increase in the error signal, characterized in , in order to increase the noise immunity, sensitivity and accuracy of the method, changing the capacitance of the undercompensation sensor eobrazuyut into alternating current output signal proportional to the offset, resulting AC signal is compared with an AC signal proportional to the reference capacitance. The resulting difference in signals is amplified, demodulated, and integrated, and the period of alternating current signals is chosen to be no less than an order of magnitude longer than the time constant for recharging the parasitic capacitances of the undercompensation sensor and the electrohydrodynamic inverse converter. i / o ivyh (rig 2.