The reason of higher temperature instrument measurement by thermocouple thermoelectric potential1

Thermocouple as a temperature instrument, can directly measure the temperature, and the temperature signals into a thermoelectric emfs, through electrical instrument ( Secondary instrument) Convert the temperature of the measured medium. Thermocouple temperature measurement is the basic principle of two kinds of different ingredients of closed loop conductor material composition, when when there is a temperature gradient at both ends, loop will have an electric current passes through, the existed between the electromotive force on both ends - — Thermoelectric emf, this is the so-called seebeck effect. With the continuous development of industry, thermocouple this temperature meter has been widely used in industrial measurement.

thermocouple in the process of temperature measurement, there may be measured thermoelectric potential higher than the actual value, then we need to find out why, here is a project to measure thermoelectric potential is higher than the actual value possible reason and repair method. 1:

may cause thermal electrode metamorphism;

repair method 1: change thermocouple;

may cause 2: compensation conductor should be in conformity with thermocouple type;

repair method 2: change compensation conductor, consistent with thermocouple type;

may cause 3: thermocouple installation method, location, or improper insertion depth ( Thermocouple installation should follow the principle of which) ；

repair method 3: install according to the specified requirements; Possible reasons for

4: insulation damage external power into the thermocouple circuit;

4: repair method to repair or replace the insulation materials; Possible reasons for

5: compensation junction between conductor and the hot electrode two different junction temperature;

repair method 5: extension of the compensating conductor makes the contact temperature is the same;

may cause 6: have the jamming signal access;

6: repair method to check interference sources, to exclude ( What are commonly used thermocouple anti-interference measures) ； Possible reasons for

7: the thermocouple reference end temperature on the high side, When measuring negative temperature) ；

7: repair method to adjust the reference temperature or making up;

the above factors are likely to cause temperature instrument measurement by thermocouple thermoelectric potential is higher than the actual value of the reason, we encounter similar situation in the practical work, you can refer to the above several aspects to do check.

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key words: thermal resistance, thermocouple, thermal resistance, platinum resistance, PT100, PT1000, pressure sensor and digital temperature sensor