Introduction to the use of thermocouples

Application of Thermocouples

(1) To reduce the measurement error, the thermocouple should be in full contact with the object being measured so that both are at the same temperature.

(2) The protective tube should have sufficient mechanical strength and be able to withstand the corrosion of the measured medium. The thicker the outer diameter of the protective tube, the better the heat resistance and corrosion resistance, but the greater the thermal conductivity.

(3) When dust and other materials adhere to the surface of the protective tube, the thermal resistance will increase, causing the indicated temperature to be lower than the actual temperature and causing deviation, so it should be cleaned regularly.

(4) The influence of magnetic induction. The signal transmission line of the thermocouple should be laid away from the strong electric area (such as high-power motors, transformers, etc.) as much as possible during wiring, and it should not be laid parallel to the power grid line at a close distance. If it is unavoidable, shielding measures should be taken or armored wires should be used, and they should be fully grounded. If you are worried about the thermocouple being affected, you can completely insulate the thermocouple wire from the protective tube and ground the protective tube.

(5) If working at the highest application temperature for a long time, you should pay attention to the change of the thermocouple material and cause deviation.

(6) Compensation and modification of cold end temperature The cold end of the thermocouple must be properly handled and kept constant. The type of compensation wire and the positive and negative poles should not be connected incorrectly. The compensation wire should not have side connections. The compensation wire should be laid separately from other wires.

(7) The welding, cleaning, regular inspection and annealing of the thermocouple should be carried out in strict accordance with relevant regulations.