SU1520330A1 - Precision capacity-to-voltage converter - Google Patents

Abstract

This invention relates to a measurement technique and can be used in capacitive primary displacement transducers. In order to increase the accuracy of the converter containing capacitors 1, 2, switches 5, 6, pulse generator 8, counting trigger 9, inverter 10, element 11 OR NOT, charge-voltage converter 12, voltage 13, reference source 14 bus, zero potential bus 16, switches 3, 4, capacitor 7, inverse source 15 of reference voltage are introduced. The feedback formed by the circuit consisting of the converter 12, the switch 3, the integrator 13 and the switch 4, restores the balance of charges on the capacitors 1, 2 and 7, while the output signal of the switch 3 decreases to zero. 1 il.

Description

one

(21) Aitl4770 / 2A-28

(22) 03/18/88

(46) 11/07/39. Bul W 41

(72) A.V. Tynov and V.I. Gorshenev

(53) 621.317.335 (088.8)

(56) Grinevich FB, et al., Technical Electrodynamics, 1980, ff 3, p. 73.

A. Cherdantsev, A. Klementyev, Capacitance-to-Voltage Transducer. - Instruments and Experimental Technique, 1984, No. 5, p. 128.

(54) PRECISION CONVERTER CAPACITIES IN VOLTAGE

(57) The invention relates to measurement technology and can be used in capacitive primary displacement transducers. With a circuit for improving accuracy in a converter containing capacitors 1, 2, switches 5, 6, pulse generator 8, counting trigger 9, inverter 10, OR-HE element 11, charge-voltage converter 12, integrator 13, reference source 14 bus, zero potential bus 16, switches 3, 4, capacitor 7, inverse source 15 of reference voltage are introduced. The feedback formed by the circuit consisting of the converter 12, the switch 3, the integrator 13 and the switch 4, restores the balance of the charges on the capacitors 1, 2 and 7, while the output signal of the switch 3 decreases to zero. 1 il.

with s

(L

ate INS

ABOUT

00

with

The invention relates to measurement technology and can be used in capacitive primary transducers of displacements.

The purpose of the invention is to improve the accuracy of the converter by eliminating the dependence of the output voltage on the initial capacitance of the measuring capacitor.

The drawing shows a block diagram of the Converter.

The converter contains measuring capacitor 1, compensation capacitor 2, switches 3-6, additional capacitor 7, generator 8 pulses, counting trigger 9, inverter 10, element OR-NOT 11, charge-voltage converter 12, integrator 13, reference source 1 voltage, inverse source 15 of the reference voltage, the bus 16 of zero potential.

The output of the source 14 of the reference voltage through the switch 5 is connected to the capacitor 2, and the output of the inverse source 15 of the reference voltage through the switch 6 is connected to the capacitor 1.

The pulses from the output of the counting trigger 9 control the operation of the switches 4-6, and the pulses from the output of the element OR NOT 11 control the operation of the switch 3.

 The converter works as follows

In the initial state, by changing the magnitude of Uo (the reference voltage of source 14 or the magnitude of Uo of the inverse reference voltage of source 15 ensure that

Ugi CK UOJ GXO. (one)

where CK, is the compensation capacity

capacitor 2J CKO initial capacity of the measuring capacitor 1.

When the measured value changes, the capacitance of the measuring capacitor 1 changes by the value of -t and Cx, driving the circuit to imbalance.

The feedback formed by the circuit consisting of the converter 12, the switch 3, the integrator 13 and the switch 4, restores the balance of charges on the capacitors 1,2 and 7, while the output signal of the switch 3 is reduced to zero.

The synchronous operation of blocks 3-6 is provided by pulses from the output of the counting trigger 9 and the element OR NOT 11.

The balance state of the converter is characterized by the following relationship:

UD-I-CX Uo (C + Ux Cf ,, (2)

Where

SA is the capacity of the additional capacitor 7. Since Cx C, taking into account expression (1), equation (2) will be simplified to .vid:

I (i

(3)

Uo2Cd

From (3) it can be seen that the output signal does not depend on the magnitude of the initial capacitance Ссо of the measuring capacitor.,

five

0

five

0

five

0

five

Claims (1)

Invention Formula Precision capacitance-to-voltage converter containing a voltage source, two switches, two capacitors, a voltage-to-voltage converter, an integrator, a pulse generator, a counting trigger, an inverter, an OR-NOT element, a zero potential bus, a reference voltage source output connected to the first information input of the first switch, whose output through the first capacitor connected to the input of the charge-voltage converter, the zero-potential bus is connected to the second information-. The first input of the first switch and the first information input of the second switch, the output of which is connected via the second capacitor to the input of the charge-voltage converter, the output of the pulse generator is connected to the first input of the OR-NOT element and through the serially connected counting trigger and the inverter is connected to the second input of the element OR NOT, the output of the counting trigger is connected to the control inputs of the first and second switches, characterized in that, in order to improve the accuracy, an inverse reference source is introduced into it second voltage, third and fourth switches, and a third capacitor, zero-potential line is connected to the first data inputs of the third and fourth switches through which vyhssch 5 1520330 the third capacitor is connected to the inlet, the outputs of the counting trigger and the inverter charge converter for example OR are NOT connected to the control, the output of which is connected to the second inputs of the fourth the information input of the third and third switches, the output of the inverter switch, the output of which through a source of reference voltage the integrator is connected to the second information-connected to the second information the fourth input switch input of the second switch.