PCB Heaven

General Category => General Discussion => Topic started by: mcm200 on April 24, 2016, 22:38:43 PM

Title: Thermocouples
Post by: mcm200 on April 24, 2016, 22:38:43 PM
Hello there! I have a question that has been haunting me for long. Recently I read over and over the thermocouple article on pcbheaven and the question arose again. Let?s see for example this situation (depicted in the TC article when cold compensation is explained): we have the TC wires attached to a pair of copper wires on the connecting isothermal block. I cannot understand why, despite of both junctions on the block being of different nature, let?s say chromel-copper and alumel-copper, this doesn?t create a source of error when both these junctions are at the same temperature  (say 0 deg C). I do understand why two junctions of  equal  nature give zero output when held at the same temperature, but not in the case of different junctions. Can anybody help me with this? Thank you !