Thermocouple is a kind of common temperature measuring instrument, the scope of application is also very extensive. Thermocouple common failure 1, failure phenomenon: digital display table indicates a negative; Possible reasons: digital display table with thermocouple wiring is wrong or thermocouple have short circuit phenomenon; Processing method: correct wiring, or find out short circuit, reinforced insulation. 2, fault phenomenon: thermocouple table indicating infinity; Possible reasons: thermocouple or loosen the lead wire short circuit or terminal; Methods: the change in resistance or welding and tighten the screw connection, etc. 3, fault phenomenon: display of thermocouple indicated value is lower than the actual value or unstable value; Possible reasons: protecting tube with metal dust, dust, dirt and thermocouple short circuit between terminal; Methods: to remove scrap metal, cleaning dust, water, etc. , find the short circuit point reinforced insulation. 4, failure phenomenon: thermocouple value changes with the temperature relation; Possible reasons: thermocouple wire material corrosion metamorphism; Deal with method: replace thermocouple;