Causes of Errors in Temperature Control Instruments of Experimental Electric Furnace
(1) According to the characteristic curve of the molded thermocouple, it can be seen that the thermoelectric potential of the two different materials constituting the thermocouple is not linear with the temperature, and some have relatively large curvatures. Therefore, using thermocouples to measure temperature and non-linear correction are also very important. Improper handling will bring errors.
(2) The thermoelectric power generated by the thermocouple is not only related to the temperature of the measuring end, but also to the temperature of the cold junction. Only when the temperature of the cold junction is constant, the thermoelectric potential is only related to the temperature of the working end. Most instruments have a cold-junction temperature compensation function. If the ambient temperature of the instrument does not change much, the error caused by the cold-junction temperature compensation can be ignored. Fully compensated, then a certain error will also be introduced. For the b-type thermocouple, since the thermoelectric potential is less than 3μv in the range of 0~50℃, temperature compensation is not required.
- It can be seen from the index table of the thermocouple that the thermoelectromotive force output by the thermocouple is very small. In order to achieve more accurate measurement, in addition to improving the precision of the measuring instrument, an external amplifier circuit is also required. , This will also introduce errors.