After the correct wiring is energized according to the instrument wiring diagram, the instrument first displays the thermocouple graduation number of the instrument, then displays the range of the instrument, and then the digital tube in the lower row of the instrument displays the set temperature, and the digital tube in the upper row of the instrument displays the measured temperature. If the digital tube on the upper row of the meter shows the temperature of the heating element instead of the heating element, but displays the condition of "OVER", "0000" or "000", it means that the input part of the instrument is faulty, and the following tests should be performed:
1) Remove the thermocouple from the meter thermocouple input, and then use any wire to short-circuit the meter thermocouple input. When the power is on, when the value displayed by the digital tube on the upper row of the meter is about room temperature, it means that the internal connection of the thermocouple is open, and the thermocouple of the same type should be replaced. If the above situation is still the same, it means that the input end of the instrument is damaged during transportation, and the instrument should be replaced.
2) remove the thermocouple of the above-mentioned fault instrument, and replace it with the thermocouple connected to the same kind of graduation number instrument that is running normally next to it, after power-on, when the digital tube on the upper row of the original fault instrument displays the temperature of the heating element, it means that the thermocouple connection is open, and the thermocouple of the same type is replaced.
3) Remove the faulty thermocouple from the instrument, use a multimeter to measure ohms (R)*1 gear, use the two meter rods of the multimeter to measure both ends of the thermocouple, if the resistance value displayed on the multimeter is very large, it means that the thermocouple is connected to an open circuit inside, and the thermocouple of the same type is replaced. Otherwise, there is a certain resistance value, which means that there is a problem with the input end of the instrument, and the instrument should be replaced.
4) According to the instrument wiring diagram wiring correctly, if the instrument is energized, the upper row of the instrument digital tube shows a negative value, etc., indicating that the thermocouple "+" and "—" connected to the instrument are wrongly connected. Just swap it out again.
5) When the instrument is in operation, the temperature displayed by the digital tube on the upper row of the instrument is 40 degrees ~ 70 degrees different from the actual measured temperature. The difference is even greater, indicating that the graduation number of the instrument is wrong with the graduation number of the thermocouple. According to the correspondence between the temperature and millivolt (MV) value of thermocouples such as thermocouple graduation number B, S, K, E, etc., under the same temperature, the millivolt value (MV) B graduation number is small, the S graduation number is small, the K graduation number is larger, and the E graduation number is judged according to this principle.