SU1582030A1 - Device for measuring temperature - Google Patents

Abstract

The invention relates to the field of temperature variations and allows for improved measurement accuracy. Two similar thermocouples of resistance (TS) 1 and 2 are connected to the first winding of a current transformer 8, the second winding of which is connected to a variable resistor 11, a constant resistor 12 and a rheochord 9, the slider of which is connected to a reversible motor 14 connected to the output of the photosensitive amplifier 13. Using switches 15-18 and a variable resistor 10, it is possible to measure the resistance of the TC 1 and the ratio of the resistances of the TC 1 and TC 2, which makes it possible to determine the change in the initial resistance of the TC 1 during operation. atsii TC. 1 il.

Description

The invention relates to temperature measurements, in particular, to automatic measuring devices operating in conjunction with resistance thermocouplers.

The aim of the invention is to improve the measurement accuracy by reducing the effect on the measurement result of a change in the parameters of the thermal converter during operation.

The drawing shows a diagram of the device.

The device contains two resistance thermocouples of the same type (TS) 1 and 2 with terminals represented by resistors 3-7, a current transformer 8, with the first and second windings of reochord 9, two variable resistors 10 and 11, a constant resistor 12. Phase-sensitive amplifier 13, reversible an engine 1A, kinematically associated with a reichord engine, and four paired switches 15-18. The device works as follows.

Temperature measurement is carried out with the help of TC 1. In this case, the switches are in the position. X}. The resistance of TC 1 is described by the expression

Rt "

de R0t (ЈQ)

Rnl (to) 0 + t)

(ABOUT

W. 0 v. «- 0. resistance TC 1 at the beginning of operation at zero temperature tj temperature coefficient.

0

where is the current in the secondary winding

transformer 1.

Over time, operation Ј changes the value of RO (), which leads to a decrease in measurement accuracy. The device is corrected when the value of R 0 (изменении) is changed by correspondingly changing the value of R "of the resistor 11. The new value of RC) is determined from the relation

RtH (t) R0i (Ј0) .f (e), (4)

5 where f (6) is a theoretically calculated or experimentally determined Function depending on a vehicle of the same material on the ratio of the wire diameters of the sensitive elements of the vehicle and the ratio of their resistances R (/ Riz) that changes during operation of the vehicle. RQ / () values, it is necessary to measure the value D for TC 1 and 2. This measurement consists of two balances of the measuring circuit. The first position is made in the switch position B. By changing the shunt resistor 10, we obtain the circuit change, which is determined by the establishment of the slide motor at any scale point, at the same time, the voltage on the thermal converters and the secondary winding of the transformer, i.e.

five

0

35

40

Before starting measurements with the help of resistor 11, a current of 1p is established through resistor 12 and rheohord 9, so that the ratio

I R-tH R o) O + t)

 Ip (+ Rg-Xo); , where I - current through TC 1;

(2)

X0 - the position of the engine Reochord

corresponding to the beginning of the account; R {Ј, R $ - resistance of resistor 12

and reohorda 9.

The value of the RU resistance of the resistor 11 can be determined from the expression:

g, (Rf + RQ). Goch

(u- IP) C3)

IT (Re + R,) IP (R n + R4),

45

50

55

where It is the current flowing through the vehicle

1 and 2, - RI and R Q - resistances of TC 1 and 2

respectively.

In this case, the currents through the resistors 7 and 5 are equal to zero. In the second automatic balancing scheme, i.e. in the position from the switches, the voltage on the TC 1 is equal to the voltage on the resistors 12 and the part of the resistor 9, i.e.

ITR (Ip (R (2+ X.Rg) (6)

where X is the position of the engine in relative units, 0 X I.

At the same time, the stresses on the second TC 2 and the second part of the reichord 9 are equal.

 ITR2 IP (1-X) R9 (7)

If we divide the expression (6) into (7), then we get the connection between the value of $ and the position of the slider

Ri Kz X

 RC R9 (i-x)

(eight)

Thus, the position of the reichord slider uniquely characterizes the value of the resistance ratio 0, which makes it possible to determine the new value R 0 (Ј).

Claims (1)

Invention Formula A temperature measuring device containing a first thermal converter of resistance, the first terminal of which is connected to the first terminal of the first winding of a current transformer and the first terminal of its second winding, connected through a first variable resistor and a series-connected constant resistor and rheochord with the second terminal of the second winding, a phase-sensitive amplifier reversible motor, kinematically associated with a reichord engine, 82030 characterized in that, in order to improve measurement accuracy, four switches are introduced into it, a second variable resistor and a second  a resistance thermoconverter, the first terminal of which is connected to the second output of the first resistance thermocoupler and connected to ... the first and third fixed contacts of the third switch, and the second output is connected to the moving contact of the fourth switch and through the second variable resistor jc is connected to the second and third fixed contacts of the first switch, the movable contact of which is connected to the first output of the first winding of the current transformer, the first input of the phase-sensitive amplifier is connected to the moving contact of the second switch, and the second input is connected to the movable contact of the third switch and the second fixed contact of the fourth switch, the third fixed contact of which is connected to the second output of the second winding of the current transformer and the second fixed contact of the second a switch, a first fixed contact of which is connected to the third fixed contact and helipot. 20 25 thirty