Thermocouple ( TC sensor) The measuring principle and temperature range tolerance

Three chang instrument thermocouple sensors generate mV measuring signal, the signal is proportional to the temperature, depending on the type of TC. Measuring principle:

when two different metal or metal alloy ( Hotline) The wire on one end, Hot junction) Together, form a thermocouple. These the free end of the wire form reference point. If the hot junction T1 T2 temperature difference between the reference points, is produced in the thermocouple thermoelectric emfs ( The mV voltage) The voltage level and temperature T1 - only T2 and thermocouple materials in proportion. By ( Seebeck effect) Composition.

so, when using the extension cord or insulation hotline will reference point moves to standard temperature ( Reference temperature) Position, it is important to make reference point as stable as possible.

cold junction compensation ( CJC)

temperature transmitter or measurement system needs reference point ( The cold end) Temperature T2 information. Through the CJC measurement ( The cold end compensation) The change of temperature compensation reference point. Temperature transmitter CJC measurement can be internal function of measuring the resistance or integrated in the connector. If the reference points away from the emitter, the must to separate temperature measuring point, and connect it to the transmitter as a compensation signal.

thermocouple type temperature range and tolerance:

* L defined in standard DIN 43710, all the other types in the standard EN 60584 - Definition 2.

thermocouple type of materials and cable:

cable material * the same as the thermocouple material or with the same electrical characteristics.

* * conform to the IEC 584 standard cable/wire color, but in accordance with DIN 43710 U and L.

figure: thermocouple cable material and color