SU1379747A1 - Device for remote measuring of resistance - Google Patents

Abstract

The invention can be used, in particular, to measure the resistance of sections in DC circuits without disconnecting the voltage. The device for remote measurement of resistance includes a link 2, generators 3 and 4 of fixed frequencies, switch 5, resistive optocouplers 6 and 7, display unit 8, resistors 9 and 10 of the shoulders of the bridge circuit, power supply 11. The sensitivity of the measurement is enhanced by eliminating the influence of link 2 on the measurement result. 2 Il.

Description

l

Oq

WITH

-J

four;

F1 / G.2

The invention relates to electrical measurements and can be used in automatic measurement and control systems of active resistance, for example, to measure the active resistance of sections in DC circuits without disconnecting the voltage.

The purpose of the invention is to measure the resistances under voltage, increase sensitivity by eliminating the influence of the communication line on the measurement result, expanding the functionality, and also simplifying the device.

None of figs. 1 shows the communication line of the measured resistance with the measuring device} in FIG. 2 is a block diagram of the device.

The device contains measured resistance 1, communication line 2, fixed-frequency generators 3 and 4, switch 5, resistive optocouplers 6 and 7, display unit 8, resistors 9 and 10 of the shoulders of the bridge circuit, power supply 11, and generators 3 and 4 fixed frequencies through switch 5 and link 2 are connected to measured resistance 1, the lamp of the first optocoupler 6 is connected in series, and the lamp of the second optocoupler 7 is connected to it in series with the resistor of optocouplers 6 and 7 with resistors 9 and 10 form a bridge measurement circuit, one of the diagonals otorrhea enabled display unit 8, and the other - the power source 11.

In Fig. 1a, the communication line is represented as a chain with distributed parameters, where Ry. R. and Е — first, second, and third sections. The resistance measurement chains L, R. С,, LA, R. A ,,, C, Bd, Nd, are the distributed parameters of the circuit; With g - coupling capacitors.

A chain with distributed parameters can be reduced to a chain with lumped parameters (Fig. 16, where Rd, C. Ld are the generalized parameters of the circuit; R l is the own active resistance of the circuit, C is the own capacitance of the circuit L, is the own inductance),

A circuit of type L is a Campbell inductance, and for an alternating current circuit it can be

in the form of effective inductance (Fig. 1c), the value of which is determined by the expression L L, - R C.

The device works as follows.

The filament lamp of the optocoupler 6 is connected in series with the load resistance 1, therefore, the luminous flux of the filament lamp is proportional to the square of the current, i.e.

F i.

L,

(one)

15

The filament lamp of the optocoupler 7 is connected in parallel with the load resistance 1, its luminous flux is equal to

20

l and

one

(2)

The resistance values of the photoresistors of the optocouplers are determined by the luminous fluxes of the incandescent lamp and are respectively equal to

F,

Kf.,

(3)

thirty

The readings of the microammeter are determined by the ratio of the resistances of the photoresistors of the bridge circuit, i.e.

, Ro, l, and

 Fd / II

Ry +.

35

Jt

(four)

0

five

where C is the capacitance of the communication line with the measuring resistance; and is the effective value of the voltage of the slump lamp 7, I is the effective value of the current through the lamp of the optocoupler 6. The measurements are carried out at two frequencies, i.e. the first measurement is carried out in position I of the switching device 5 and corresponds to the frequency w, and the second is carried out in position II of the switching device and corresponds to the frequency s, hence, taking into account (4), we can write

,

V7

+ and L

ZF

(five)

55

one

+ W.

E4

where C is the capacitance of the communication line with the measured resistance.

Sola system of equations (1) for R.

get

R,

(c / i Vi-с, Ы;)

)

ten

noting that, for an hour, the readings, the setting of the equipotential bridge can be reduced to a, the frequencies cj, and the values are backwards and are constant,

as well as the value of the capacitance of the connection C, jj and indicator, are

A device for measuring the resistance of two generators fik connected through connected switching of the communication to one of the neither measured nor with the source

In order to increase the sensitivities, two opto-measuring circuits are inserted into the sensor, to connect the connection of the first optimeter to the resistive resistor, the incandescent link to the resistor, and the photodiode is included in the differential of the bridge circuit measuring diagonals of which Guyu - indicator.

R

Where

Thus, the resistance value of the measured section of the circuit is determined by the indications of the micro-ammeter of the pointer t, and the components of the reactance of the communication line, according to the extrusions (7) and (8), do not affect the measurement result. The constant term D is not dependent10

, jj marriages and indicator,

20

25

thirty

sieves from measurement parameters and does not affect accuracy.

Claims (1)

Invention Formula A device for remote measurement of resistances, containing two generators of fixed frequencies, connected through a series-connected switch and a communication line to one of the terminals for connecting the measured resistance, and also the source of measuring voltage, which in order to measure the resistances under voltage Two optocouplers and bridge measuring circuits are inserted into it and increase its sensitivity, with the other terminal for connecting the measured resistance connected to the incandescent lamp The optocoupler, parallel to the measurable resistance, is included the incandescent lamp of the second optocoupler, the communication line is connected to the measured resistance by means of coupling capacitors, and the photoresistors of the optocouplers are included in the differential arms of the bridge measurement circuit, in one of the diagonals of which the measuring voltage source is connected, and in the other - the indicator. 1 L North cg