SU1120181A1 - Thermocouple for measuring low temperatures - Google Patents

Abstract

1. TERMOPAR LH DIMENSIONS OF LOW TEMPERATURES, containing a negative electrode, are made of an alloy of copper-based alloy containing an amount of 0.01-0.5 wt.% And a positive electrode, which, in order to improve measuring low temperatures by obtaining close to zero sensitivity at 273 K, the positive electrode is made of a copper-based alloy with the following ratio of components, wt.%: Nickel 0.01-3.5 Copper Rest 2. Thermocouple according to claim 1, о tl and h and y and a tag with that negative electro d, made of an alloy on 9 based on copper, additionally contains lithium in the amount of 0.0005-0.05 wt.%. GO o 00

Description

1 The invention relates to thermometry, in particular to the measurement of low temperatures using thermocouples. A known thermocouple for measuring low temperatures, containing a negative electrode made from a copper-based alloy and a positive electrode tl 3. However, the thermocouple has considerable sensitivity near the rotate temperature, therefore, with reference temperature peaks exceeding fractions of a degree, the temperature is measured with great humility. In addition, stabilization of the temperature of the reference junction requires the use of energy-intensive and bulky equipment, which is not always possible under the conditions of aviation and space technology. The closest to the present invention is a thermocouple for measuring low temperatures, containing a negative electrode made of copper-based alloy containing 0.01–0.5 wt.% Iron and a positive t2T electrode. In a thermocouple, the sensitivity of thermoelectrodes is significantly reduced at 273 K and is in the order of 0.6 µV / degree. However, with the current metrological support of a number of areas of new technology, it is necessary to further improve the accuracy of measurements of csherats, which can be achieved by further reducing the sensitivity of the thermocouple near 273 K. The purpose of the invention is to increase the measurement accuracy by getting closer to zero sensitivity at 273 K.: The goal is achieved by the fact that in a thermocouple for measuring low temperatures, containing a negative electrode made of an alloy based on copper containing iron in an amount of 0.01 -0.5 wt.% And a positive electrode, the positive electrode is made of an alloy based on copper with the following quantitative ratio of components, bcc.% :. Nickel 0.01-3.5 Copper Else 1 Negative electrode made of an alloy based on copper, additionally contains lithium in the amount of 0.0005-0.05, wt%. Thermocouple works as follows. The positive electrode in the developed thermocouple has a small differential thermo-EMF at 4-77 K and a relatively large one at 273-300 K, and the sign coinciding with the thermopower of the copper – iron alloy. As a result, the thermo-EMF pair in the region (4-77 O is large, and in the range of (273-300) K, the selection of electrode materials makes it possible to achieve almost zero sensitivity of the thermocouple to the temperature of the free ends, for which the thermoelectric sensitivity of the two electrodes at 273 K should coincide. coziness, so that the emf of the pair is zero. The iron content in the negative electrode, depending on the purpose of the thermocouple, varies from 0.05 to 0.5%. At the same time, the absolute differential thermo-emf at 273 K can range from +1.6 to -12.5 µV / / degree The copper alloy with nickel gives the same thermo-emf with a nickel content of between 0.01 and 3.5%, respectively .The thermoelectric 1hc heterogeneity of the positive electrode provides the temperature measurement offered by the thermocouple with an accuracy of 0.1 degrees. A positive electrode based on a copper-nickel alloy with a nickel concentration of less than 0.01% has an absolute differential thermo-emf of 010.1 µV / deg over the entire range of 4.230 K and is not of practical interest. The alloy-copper-nickel with a nickel content of more than 3.5% has thermoelectric non-uniformity, giving an error in determining the temperature of more than 0.1 degrees. The table shows the values of thermo-EMF coefficients of thermocouples made from known and proposed thermoelectrodes with different content of ingredients included in the alloy.

+ 0.01 Fe +, 0.15 Fe + 0.50 Fe 0.15 Fe + 0.002 Li

Cu + 0.01 Fe

Cu + 0.15 Fe

Cu + 0.50 Fe

Cu + 0.10 Fe + 0.003 Li + 0.10 Fe + 0, OP05 Li + 0.10 Fe 4- 0.05 Li + 0.15 Fe + 0.003 Li

one

five

eight

ten

13

7

eight

ten

0.1

five

0, t

ten

7

0.15

0.1

ten

0.15

ten

/

0.15

10 15

0.15

The table shows that the proposed thermocouple is not inferior to the known. sensitivity at cryogenic temperatures and has almost zero sensitivity at the temperature of melting ice. This allows for most technical measurements to refuse temperature control of free ends, since the change in their temperature is in the range of up to. 20®C does not affect the integral thermo-EMF, which helps reduce the cost of control and measuring; Staff: Tours and Reduce Energy Consumption.

Claims (2)

1. Thermocouple D1 AND MEASUREMENTS OF LOW TEMPERATURES, containing a negative electrode made of an alloy based on copper containing iron in an amount of 0.01-0.5 wt.%, Th positive electrode, characterized in that, in order to improve the accuracy of measuring low temperature by obtaining a sensitivity close to zero at 273 K, the positive electrode is made of an alloy based on copper in the following quantitative ratio of components, May.%: Nickel 0.01-3.5 Copper Else 2. The thermocouple according to claim 1, according to the fact that the negative electrode, made of an alloy based on copper, additionally contains lithium in the amount of 0.0005-0.05 wt.