Thermocouple not constant solution

In the use of thermocouple most are used for temperature measurement, a lot of industrial production, are inseparable from the use of thermocouple, but many people still do not understand the use of thermocouple knowledge, so let's introduce this knowledge for us in detail.

For thermocouples used as reference and specifications, annealing should be performed after each point during indexing. The annealing procedure is very important for precious metal thermocouples. In the standard thermocouple verification rules, the standard thermocouple must be cleaned and annealed before verification, in order to eliminate the contamination and stress of the thermocouple, and then improve the metallographic structure of the couple wire material, to achieve the stability of the progressive measurement.

In the process of thermocouple production, the couple wire is always stained on its surface after multiple diameter reduction drawing. At the same time, from the even wire internal structure. Inevitably there are stresses and lattice inhomogeneity. These physical inconsistencies have an effect on the Seebeck coefficient of the couple wire, which affects the instability of the thermocouple indicator value. Therefore, a thermocouple with unqualified annealing cannot be used for accurate temperature measurement.

Stress introduced by quenching or cold working can be basically eliminated by annealing. The value error caused by unqualified annealing may vary from several tenths of a degree to several degrees. It is related to the temperature to be measured and the temperature gradient on the thermocouple electrode. Cheap metal thermocouple wire is usually "annealing" condition delivery, if the need for high temperature with cheap metal thermocouple annealing, then the annealing temperature should be higher than the upper limit of the temperature, insertion depth should be greater than the actual use of depth.