SU1594450A1 - Capacitor parameters-to-voltage converter - Google Patents

Abstract

The invention relates to electrical measuring equipment and can be used to measure the parameters of a capacitive sensor with a dielectric method for monitoring the parameters of materials. The purpose of the invention is to increase speed. The capacitor voltage to voltage converter contains a generator 1, an operational amplifier 2, a voltage divider 3, a subtraction unit 4 and a phase detector 5. Introduction to the converter of a regulator 6 and a dual variable resistance 7 automates the process of converting and simultaneously measuring voltages proportional to capacitance CX and active conductivity G X. 2 Il.

Description

The invention relates to electrical measuring equipment and is intended to measure the parameters of capacitors having dielectric losses, for example, capacitive sensors used in the dielectric method of controlling the quality of materials

Pel invention - increase speed,

Figure 1 presents the functional diagram of the Converter; fig 2 is a functional diagram of the regulator and controlled resistance.

The capacitor voltage to voltage converter contains a generator 1, a first operational amplifier, U1b 2, a voltage divider 3, a subtraction unit 4, a phase detector 5, a regulator 6, a dual variable resistance 7, a second operational amplifier 8.

The converter works in the following manner: -.

The output voltages of the generator 1 O and the subtraction unit 4 U are interconnected by the dependence

, and, (1-f -1- ° -) -and

. ,. | .-

 and B. .li. K7 T (

jarcig-cJ RxC-x

e

 j av- cf wR c7

Jifici

Rj

x

l + jwRjfC

 Rx

.jarci u) RxCx

{

five

0

five

0

five

If the phase shift angle between the voltages at the inputs of the phase detector is different from zero, a voltage appears at its output, the value of which depends on the magnitude and sign of the error angle. This voltage, proportional to the error, is rejected by the regulator, at the output of which a control action appears that changes the resistance of the resistor R until 5

  RO 0

Control effect on K and R

 /} the controller is generated in the following way. When the device is turned on, the output voltage of the regulator is a and 0, R is darkened. At full

and fi.

the darkened resistor R is ahead of U,, since R Cd, therefore, arctgW R {, CQ arctf wRjfC. Let the voltage at the output of the phase detector 5 have a plus sign. Then at the output of the regulator for the Vits voltage varying according to the law

С - capacitance of an exemplary capacitor;

P j are the capacitance and loss resistance of the measured capacitor of the voltage divider 3, respectively;

R - functional resistance

but coupled resistors of dual variable resistance 7; and. - input voltage of block 4,

° lj.

one

RO- e

I + JWR; C,

) RJ. S ,,

jwCe

|. I + CU (

40

and RC

j u dt.

five

0

five

This voltage will increase, the light output of the optocoupler also increases, the resistance decreases, and the voltage at the regulator input decreases with decreasing phase unbalance. This will occur until the condition, |, C; f.

In this case, the voltage at the input of the regulator and O, and the voltage at its output II (t,) - - J U dt (where tj is the phase phase) is different from zero (due to the voltage up to which the capacity C was charged). When RJJ or Sd changes, for example when increasing, the phase difference, arctg, K (, arctg. At the same time, the output of the phase detector 5 appears

and

tricate polarity U, and at the output of the regulator, the voltage U is changed according to the law

one

and (t) u (t,) J and dt,

about

those. will decrease in magnitude, which will lead to a decrease in the light output of the optocoupler and an increase in R. The process will continue until the condition is met, which is both negative and non-zero. A positive polarity voltage u cannot appear in the circuit, since as u decreases in modulus and corresponds to it, the change in the light flux of the optocoupler always finds negative polarity and the corresponding resistance of the resistor R at which RpCg RyCx.

Thus, the polarity of the output voltage of the regulator does not change during operation. In this case, the phase shift angle between the voltages at the inputs of the phase detector becomes zero. Thus, the voltage phase at the output of the subtraction unit is maintained by the controller by changing the resistance of the .RO resistor to the generator voltage phase. The voltage at the output of block 4 subtraction is equal to

t t t t H

3 and -R;

or, taking into account that, in the case of the synphase of the voltages U and U

RO

Cx

 c7

we get for voltage modules

П - У1 г К Г 3 с „X

where K, p is a constant value, ° the value of which

known in advance. I

Thus, the voltage at the output of the subtraction unit is proportional to the measured capacitance.

Voltage 1b at the output of the second opamp 8 is connected With voltage U, as follows:

T7 -5 ° "- TI °

UZ p - I, R.

R

wasp

t

Bearing in mind that in a dual variable resistor, the resistances R and R change synchronously, i.e.

Ri

D) ii

 To const.

dl and get

ten

U, U, K, R ,, ---,

15

20

25

where G --- is active conductivity

 a capacitor;

.2Rg. - the value is constant and known in advance.

Thus, the voltage at the output of the second opamp is proportional to the active conductivity of the capacitor.

The positive effect is to significantly reduce the conversion time by automating the process and simultaneously obtaining information about the value of the parameters of the capacitor S. and G.

Formula of invention

A converter of capacitor parameters to voltage containing a generator, a first operational amplifier, a subtraction unit, a phase detector, and a generator output connected to the non-inverting input of the first operational amplifier, the first input of the phase reading unit, the second input which is connected to the output of the first operational amplifier, the inverting input of which is connected to the middle point of the voltage divider connected to the output of the first operational amplifier and consists of capacitor and terminals for connecting the measured capacitor, the second terminal for connecting the measured capacitor is connected to the zero bus, characterized in that, in order to increase speed, a regulator, a dual variable resistance, a second operational amplifier and a reverse resistor connection, connected between the output and the inverting input of the second operational amplifier, non-inverted; 1st input of which is connected to the common bus, the first dual variable resistance resistor is connected to the parallel no exemplary capacitor, the second resistor

a dual variable resistance is connected between the output of the subtraction unit and the inverting input of the second operational amplifier; the control input of the dual variable resistance is connected to the output of the regulator, the input

which is connected to the output of the phase detector, the second input of which is connected to the output of the subtractor and is the first output of the device, the output of the second operational amplifier is the second output of the device.

Claims (1)

Claim A converter of capacitor parameters into a voltage containing a generator, a first operational amplifier, a subtraction unit, a phase detector, the generator output being connected to the noninverting input of the first operational amplifier, the first input of the phase detector and the first input of the subtracting unit, the second input of which is connected to the output of the first operational an amplifier, the inverting input of which is connected to the midpoint of a voltage divider connected to the output of the first operational amplifier and consisting of an exemplary the capacitor and terminals for connecting the measured capacitor, the second terminal for connecting the measured capacitor is connected to the zero bus, characterized in that, in order to increase the speed, 50 regulator, dual variable resistance, second operational amplifier and feedback resistor connected between the output and the inverting input of the second operational amplifier, the non-inverting input of which is connected to the common bus, the first dual variable resistance resistor is connected parallel to the reference capacitor, the second resistor 1594450 dual variable resistance is connected between the output of the subtraction unit and the inverting input of the second operational amplifier, the control input of the dual variable resistance is connected to the output of the regulator, the input which is connected to the output of the phase detector, the second input of which is connected to the output of the subtraction unit and 5 is the first output of the device, the output of the second operational amplifier is the second output of the device