SU1307392A1 - Resistance-to-voltage converter - Google Patents

Abstract

This invention relates to electrical measuring technology and may be. jri is used in measuring parameters of resistors, capacitors, inductors. Introduction to the converter (P) of blocks 6, 7 of the subtraction, voltage converter 8 and comparator 9 improves the reliability of the results of conversion of resistance (C) to voltage by eliminating the influence of the terminals of the contact block on the output voltage P and controlling the magnitude of the voltage drop on C terminals of the contact block 4. 1 Il. l l ate x u u u u

Description

The invention relates to electrical measuring equipment and can be used in measuring the parameter of resistors, capacitors and inductors.

The purpose of the invention is to increase the accuracy and reliability of the results of conversion of resistance to voltage by eliminating the influence of the resistance of the terminals of the contact block on the output voltage of the converter and controlling the magnitude of the voltage drop on the resistances of the terminals of the contact block.

The drawing shows a structural diagram of the proposed Converter.

The impedance-to-voltage converter contains a voltage source 1, the first output 1.1 of which is connected via an exemplary resistor 2 ((RQ) with the inverting input of the operational amplifier 3 and the first terminal 4.1 of the four-clamping contact block 4, the second output 1.2 of source 1 of the reference voltage A non-inverting input of the operational amplifier 3 is connected to the housing. The measured object 5 is connected to the converter circuit by a four-terminal contact block 4 as follows: first clamp 4.1c and second clamp 4.2. clock unit 4 is connected to the inverting input and output of the operational amplifier 3, the third terminal 4.3. and the fourth terminal 4.4. are connected to the inverting and noninverting inputs of the first subtraction unit 6. The output of the operational amplifier 3 and the output of the first subtraction unit 6 are connected to the inverting and non-inverting inputs of the second subtraction unit 7, the output of which in turn is connected to the input of the voltage converter 8. The output of the voltage converter 8 is connected to the input of the comparator 9.

The resistance to voltage converter operates as follows.

When converting the impedance Z to voltage, the current through the measured object 5 is equal to

V - UBX I - --g-;

(one)

where and R.

reference voltage, resistance of the reference resistor.

The relation (1) will be fair provided that the input resistance of the first subtraction unit 6 is many times greater than the resistance

one

measured object

6 ..

103

 X man

(2)

where Z riiax ODU PV maximum

resistance values measured by the converter.

Taking into account the high input resistance of the first block 6 of the subtraction and the ratio (1) the voltage between the fourth 4.4 and third 4.3 terminals of the contact block 4 (the voltage on the measured object 5) will be equal to

 I-z and

in

Zx

R.

(3)

where Z is the impedance

measured object. This voltage will be allocated at the output of the first subtraction unit 6 and is the output voltage of the converter.

Ub. -Zx K „

(four)

From formula (4), given that the values of and gy and RQ are known in advance, it can be said that the output voltage Ugjj, the converter, is directly proportional to the value of the transformed resistance Zy and does not depend on the value of the transient resistances of the terminals of the contact device.

The output voltage of the op amp 3 is

i, i Cz., + g „+ g,„)

Ki

Zx UBIC Sgk, + kgk)

and

out

R c in

TO.

UBX (Hz, + g, 2.)

R.

and

out

+ and

sir

to j

(five)

where r and. contact resistance of the first 4.1 and 4.2 clamps of the contact block 4,

and

IGU

 - in (C + Gkg)

R.

pada of

voltage on the transient resistance G |, and the first and second terminals of the contact block 4.

Relationships (1), (3), and (4) are valid when the output voltage of the operational amplifier 3 does not exceed (in absolute value) a certain value, at which the output transistors of the operational amplifier exit active mode and input t in saturation mode.

From the relation (5) it follows that the voltage Uj at the output of the operational amplifier 3 is equal to the vector sum

output voltage U

6X1X

transducer and voltage drop at the terminals of the contact block. Given the maximum allowable voltage value at the output of the operational amplifier, at which relations (1), (3) and (4) and max-20 are still valid, into the negative circuit, the maximum value of the output voltage of the converter for the measured resistance range, It is possible to determine the maximum allowable voltage drop across the transient contact resistances. By comparing with this voltage the voltage drop across the resistances of the transient contacts at the time of measurement, one can judge the reliability of the conversion result.

The voltage at the output of the second subtraction unit 7, taking into account ratio (5), will be equal to

and

Gy

g

 i (r

Kl

+ yr)

From relation (6) it follows that this voltage is equal to the voltage drop on the transient resistances of the terminals of the four-terminal contact device with a minus sign. Transition resistances r,., And r ,,, the third 45th house of the first subtraction unit, input

KZK 4

4.3 and fourth 4.4 terminals of the contact unit 4 are connected in series with the high input resistance of the first subtraction unit 6 and do not affect

the voltage converter unit is connected to the output of the second unit in the reading, the comparator input is connected to the voltage converter output

Editor A, Revin

Compiled by N, Mikhalev

Tehred L. Serdyukova Proofreader M. Demchik

1628/45

Circulation 731 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Project, 4

on the output voltages of the converter and the operational amplifier 3.

The voltage converter 8 converts a variable voltage U into a proportional constant voltage, which is compared with a constant voltage proportional to the maximum allowable voltage drop at the terminals of the contact device by the comparator 9. The level of the logic signal U at the output of the comparator 9 indicates the quality of contact at the time of measurement, and therefore, the reliability of the conversion results. P-rmula of the invention

Resistance to voltage converter, content reference voltage, operational force

which connection is the measured object turned on, and the inverting input is connected through an exemplary resistor to the first output source of the reference

 voltage, non-inverted input and a second output of the source of the reference voltage are connected to a housing, characterized in that, in order to improve the accuracy and reliability of the conversion results, the first and second subtraction units, a voltage converter and a comparator are inserted, the first and second terminals for connecting the measured

35 objects are connected to the inverting input and output of the operational amplifier, the third and fourth terminals for connecting the measured object are connected to the inverting and non-inverting inputs of the first subtraction unit, the inverting and non-inverting inputs of the second subtracting unit are connected respectively to the output of the operational amplifier and the output converter. with the output of the second subtraction unit, the comparator input is connected to the output of the voltage converter.

Claims (1)

Formula of the invention A resistance to voltage converter containing a reference voltage source, an operational amplifier, the measured object is included in the circuit of negative communication processing of which the inverting input is connected via a reference resistor to the first output of the voltage reference source, the non-inverting input and the second output of the voltage reference source are connected to the housing , characterized in that, in order to improve the accuracy and reliability of the conversion results, the first and second subtraction blocks are introduced into it, a voltage converter and a comparator, the first and second terminals for connecting the measured object are connected to the inverting input and output of the operational amplifier, the third and fourth terminals for connecting the measured object are connected to the inverting ;, 'and non-inverting inputs of the first subtraction unit, inverting and non-inverting inputs the second subtraction unit are connected respectively to the output of the operational amplifier and the output of the first subtraction unit, the input of the voltage converter unit is connected to the output second subtraction unit, the comparator input is connected to the output of the voltage converter