Reasons for unqualified use of thermocouples

Thermocouple output fault judgment method

1) After accurate wiring according to the meter wiring diagram, the meter first displays the thermocouple graduation number of the meter, then displays the scale of the meter, and then measures the digital tube in the lower row of the meter to display the set temperature, and the digital tube on the upper row of the meter displays the measured temperature. . If the digital tube on the upper row of the instrument displays the temperature of the heating element instead of the temperature of the heating element, but displays the status of "OVER", "0000" or "000", it means that the output part of the instrument is faulty, and the following review should be made:

A) Remove the thermocouple from the thermocouple output terminal of the instrument, and then use any wire to short-circuit the thermocouple output terminal of the instrument. When the power is turned on, when the displayed value of the digital tube on the upper row of the meter is about room temperature, it is explained that the external connection of the thermocouple is open, and the thermocouple of the same type should be replaced. If it is still in the state mentioned above, it is explained that the output end of the instrument is damaged during the transportation process, and the instrument should be replaced.

B) Remove the thermocouple of the above faulty instrument and replace it with the thermocouple connected to the instrument with the same graduation number that is running normally next to it. The external connection is open circuit, replace the thermocouple of the same type. If it is still in the state mentioned above, it means that the output end of the instrument is damaged during the transportation process, and the instrument should be replaced.

C) Remove the faulty thermocouple from the meter, use the multimeter to measure the ohm (R)*1 gear, and use the multimeter to measure the two ends of the thermocouple. If the resistance value displayed on the multimeter is very large, explain If the external connection of the thermocouple is open, replace the thermocouple of the same type. Otherwise, there is a certain resistance value, explaining that there is a problem with the output end of the meter, and the meter should be replaced.

2) The wiring is accurate according to the wiring diagram of the meter. If the digital tube on the top of the meter displays negative values after the meter is powered on, it is explained that the thermocouple "+" and "-" connected to the meter are connected incorrectly. Just replace it.