thermocouple of basic law

Thermocouple has four basic laws

One is the homogeneous conductor Law: if the two thermoelectric poles in the thermocouple circuit are of the same material, regardless of the temperature of the two contacts, the thermoelectric EMF is zero. According to this law, we can check whether the composition of two thermoelectric electrode materials is the same, and also can check the uniformity of thermoelectric electrode materials.

The second is the law of intermediate conductor: when the third conductor is connected into the thermocouple circuit, as long as the temperature of the two contacts of the third conductor is the same, the total thermoelectric EMF in the loop remains unchanged. It makes it convenient for us to directly connect various types of display instruments or regulators in the loop, or insert the two ends of thermocouple directly into liquid metal or weld directly on the surface of metal for temperature measurement.

The third is the standard electrode law: if the thermoelectric EMF produced by the thermocouple composed of two kinds of conductors and the third conductor is known, then the thermoelectric EMF generated by the thermocouple composed of the two conductors is known. As long as the thermoelectric EMF of the thermocouple composed of various metals and pure platinum is measured, the thermoelectric EMF of the thermocouple composed of various metals can be calculated directly.

The fourth is the law of intermediate temperature: the thermoelectric EMF of the thermocouple at the two contact temperatures T and t0 is equal to the algebraic sum of the corresponding thermoelectric EMFs of the thermocouple at the contact temperature of T, TN and TN, t0. The law of intermediate temperature provides a theoretical basis for the use of compensating conductors.