Four basic principles of thermocouple

1, the law of homogeneous conductor

by the same kind of homogeneous material, A conductor or semiconductors) Welding on both ends of a closed loop, whatever how conductor cross section and the temperature distribution, will not produce contact potential, temperature potential phase offset, loop total potential is zero.

visible and thermocouple must be made up of two different homogeneous conductors or semiconductors. Jorge electrode material uneven, because temperature ladder, will produce the attached heating electric potential.

2, conductor among law

in the middle of the thermocouple loop access conductor ( The third conductor) , as long as the middle temperature is the same on both ends of the conductor, the introduction of the center conductor has no effect on the thermocouple loop total potential, this is the law of conductor in the middle.

application: according to the law of middle conductor in thermocouple temperature measuring actual applications, often takes the form of hot side welding, cold end open circuit, the cold end by the wires are connected to the display instrument constitutes a temperature measuring system.

there are fears that connected with copper wire thermocouple cold end to read mV values, the conductor and thermocouple junction of contact potential measurement causes additional error. According to this law, it is not the error!

3, intermediate temperature law

two contact thermocouple loop ( Temperature T, T0) Between thermoelectric potential, equal to the thermocouple in the thermoelectric potential when temperature T, Tn and when the temperature of Tn, T0 algebra and thermoelectric potential. Tn said the middle temperature.

application: as the thermocouple E - Usually non-linear relationship between T, when the cold end temperature of 0 degrees Celsius, cannot use the known loop real thermoelectric potential E ( t, t0) Directly look-up table to calculate the temperature value of hot end; Also can't use the known loop real thermoelectric potential E ( t, t0) Direct look-up table to calculate the temperature value, plus the cold end temperature to determine the measured temperature value of hot end, should be carried out according to the laws of the intermediate temperature correction. Beginners often not according to the law of middle temperature to fix!

4, reference electrode law

it's law is a professional research, attention, general production, use the link, do not know much about simple explanation is: made from high purity platinum wire standard electrode, assumes that the nickel chrome - Nickel chrome thermocouple is negative, respectively, and the standard electrode pairs, their value is equal to the sum of the nickel and chromium - The value of nickel and chromium.