1. After accurately wiring and powering on according to the instrument wiring diagram, the instrument first displays the thermocouple graduation number of the instrument, then displays the instrument range scale, 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 display on the instrument panel shows a status such as "OVER", "0000" or "000" instead of the temperature of the heating element, it indicates that there is a fault in the output part of the instrument. The following checks should be performed:

(A)、 Remove the thermocouple from the output end of the instrument thermocouple and short-circuit the output end of the instrument thermocouple with any wire. When powered on, if the value displayed on the digital display on the instrument panel is about room temperature, it indicates that the external connection of the thermocouple is open and should be replaced with a thermocouple of the same type. If the above state persists, explain that the output end of the instrument was damaged during transportation and needs to be replaced.

（B）、 Remove the thermocouple from the faulty instrument mentioned above and replace it with a thermocouple connected to the same type of scale instrument that is running normally next to it. After powering on, if the digital display on the upper row of the faulty instrument shows the temperature of the heating element, explain that the external connection of the thermocouple is open and replace it with a thermocouple of the same type. If the above state persists, explain that the output end of the instrument was damaged during transportation and needs to be replaced.

（C）、 Remove the faulty thermocouple from the instrument, use a multimeter to measure the ohm range, and use two multimeter sticks to measure the two ends of the thermocouple. If the resistance value displayed on the multimeter is very high, it indicates that the external connection of the thermocouple is open, and replace it with a thermocouple of the same type. Otherwise, if there is a certain resistance value, it indicates that there is a problem with the output terminal of the instrument and the instrument should be replaced.

2. According to the instrument wiring diagram, the wiring should be accurate. If the digital display on the upper row of the instrument shows negative values or other phenomena after the instrument is powered on, explain that the thermocouple "+" and "-" connected to the instrument are connected incorrectly. Just replace it with a new one.

3. Accurate wiring: When the instrument is in operation, the temperature displayed on the digital tube on the upper row of the instrument may differ from the actual measured temperature by 30oC~60oC, or even more, indicating that the scale mark of the instrument is incorrect compared to the scale mark of the thermocouple. According to the correspondence between the temperature (oC) and millivolt (MV) values of thermocouples with scale marks B, S, K, E, etc., under the same temperature (oC) state, the millivolt (MV) value that occurs is the smallest for scale marks B, the second smallest for scale marks S, the largest for scale marks K, and the largest for scale marks E. This principle should be followed for judgment.