Method to compensate the wire thermocouple cold junction compensation _ instrument
1, ice bath method: commonly used in the laboratory, the reference end temperature in constant 0 degrees, but high cost, difficult to do.
2, the cold end temperature correction method: commonly used in the request is not high, when the cold end can't constant temperature of 0 degrees, requires indicating value of compensation conductor should be corrected.
Easy to do but the error is bigger.
3, compensation bridge method: less used alone, is the use of electric potential generated by unbalanced bridge to compensation thermocouple cold junction temperature change caused by the thermoelectric potential value.
Compensation bridge has a separate product, also have to do within the compensating conductor.
4, compensation conductor: it is a commonly used method, that is, extended the thermocouple cold end temperature leads to a stable place (
Usually a control room)
And then adjusted by artificial cold end temperature, namely the instrument zero to room temperature, or by the instrument for automatic compensation circuit.
For precious metal thermocouple extended the thermocouple is impossible, because the price is not high, just use the thermoelectric properties of base metals for extended conductor, middle temperature rule is applied the theoretical foundation of the compensating conductor.
Compensation conductor does not automatically compensate the change of the thermocouple cold end temperature, only the thermocouple cold end temperature leads to a stable place, compensation by artificial and instrument.
Therefore compensation conductor should be called thermocouple extension, so as not to cause the wrong understanding to the person.