1. If two wires of different materials are joined at one point and then subjected to a temperature, then a voltage difference will be generated between the open ends of the two wires. In order to be able to measure the temperature at the junction, the temperature at the open end must be known. If the temperature of the open end is not known, then it must be extended (by a compensation cable) into the zone of known temperature (reference junction, usually referred to as the "cold junction").
2. The temperature of the reference junction must be known and constant. The exact temperature is equal joind junction temperature plus cold junction temperature..
1. N type: -250 ℃ ~1260℃. 2. K type: -200 ℃ ~1260℃. 3. J type: -40 ℃ ~760℃. 4. E type: -200 ℃ ~870℃. 5. T type: -200 ℃ ~370℃.