SU777475A1 - Temperature measuring method - Google Patents

Description

(54) METHOD OF TEMPERATURE MEASUREMENT

one

The invention relates to methods for measuring the temperature of thermoelectric termeters with thermocouples.

A known method for measuring temperature involves inserting a thermocouple spa into the medium, the temperature of which is measured, and recording the thermal electromotive force (thermo-emf) that occurs at the ends of thermocouple 1.

Since the dependence of thermo-EMF on temperature is substantially non-linear, when measuring temperature, it is necessary to carry out a preliminary calibration of the fiyteivi thermocouple to remove the calibration curve with its periodic testing.

The closest to the invention in its technical nature is a method for measuring temperature, which consists in introducing a thermocouple spa into the medium whose temperature is measured, and recording the value of the thermoelectromotive force of the thermocouple, in which the thermopower conversion characteristic is linearized by introducing a compensating voltage from an additional thermocouples 2.

This method allows the linearization of the conversion characteristic, but does not allow it to stabilize over time. Linearization accuracy is low.

st i

1 mi

; (and G (f.

since it depends on the nonidentity of the parameters of the measuring and additional thermocouples, is carried out in a narrow range, the values of the measured temperatures.

The aim of the invention is to improve the range of measured temperatures and increase measurement accuracy.

The goal is achieved by the fact that after registering the value of the measured

10 thermoelectromotive forces heat the junction of the thermocouple by passing a current through the thermocouple, register the set value of the thermoelectromotive force, determine the ratio of registered

15 values of ter: moe-electromotive forces, and the desired temperature is determined by the formula,

in Mk-)

20

target temperature;

Peltier coefficient;

l /

junction current

thermocouples;

25

.

 the relative values of the registered thermoelectromotive forces EI and EZ before and after heating;

30 thermal conductivity spa.

BUT

The essence of the proposed method is as follows.

Initially, the value of thermo-emf of a thermocouple developed under the action of temperature 9 is recorded:

(one)

I, l0, + v0 + Sie ,,

where A, B, C are constant coefficients, for EE is different from the material of the thermocouple;

 A + 2BQi + ZSE -

S, dWi

The sensitivity of the thermocouple at the operating point of the conversion characteristic defined by the Oi value.

Then an electric current is passed through the heated junction of the thermocouple. Due to the Peltier effect, additional heat is released in the junction, which overheats the junction. .The resulting spa temperature is set to 62 01 + Dv, where Dw is the temperature of the spa overheating relative to the measured temperature B, which is determined by

expression. /. With this thermo-emf

The thermocouple becomes equal to 2 52 (61 + + Dv), where 2 is the sensitivity corresponding to the new value of temperature 62. Due to a small temperature increment, the sensitivity of the thermocouple remains almost unchanged, i.e. S2 Si, therefore the increment of thermo-EMF of the thermocouple is:

& E E2-Ei 5, De S, .- /.

Thermo-EMF, developed by thermocouple at a temperature of spa 82, is equal to:

-E2 AE 5,

The following is the ratio of the values of thermo-emf:

  ()

The desired temperature is determined by the formula derived from (5) with regard to expressions (2) and (4):

 temperature measurement accuracy does not depend on the sensitivity of the thermocouple Si, determined by the coefficients A, B, C of the characteristics of the thermocouple, but is determined by the accuracy of measurements of the quantities / A that can be measured with high accuracy.

When measuring the temperature by the proposed method, the accuracy of temperature measurements increases, the range of measured temperatures is expanded.

Claims (2)

1.Turichin A.M. Electric measurements of non-electric quantities. “Energia, M.-L. .. 1966 p. 111. 2. USSR author's certificate number 498513, cl. G 01 K 7/02, 08.06.73 (prototype).