Thermocouple output fault judgment method - Database & Sql Blog Articles

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1) According to the wiring diagram of the instrument, after accurate wiring, the meter first displays the thermocouple index number of the meter, then displays the scale of the meter, and then measures the set temperature of the digital tube in the lower row of the meter. The digital tube on the meter displays the measured temperature. . If the digital tube on the meter displays the temperature of the heating element and displays the status of “OVER”, “0000” or “000”, and the output of the instrument is faulty, it should be reviewed as follows:

A) Remove the thermocouple from the meter thermocouple output and short-circuit the meter thermocouple output with any wire. When the power is on, the value of the digital tube on the meter is about room temperature. Explain that the external connection of the thermocouple is open, and the thermocouple of the same type should be changed. If it is still the above state, interpret the instrument in the transportation process, the output of the instrument is destroyed, 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 of the same type of indexing instrument that is running normally. After the power is turned on, the digital tube of the original faulty meter displays the temperature of the heating element, explaining the thermocouple. The external connection is open and the same type of thermocouple is changed. If it is still the above state, interpret the instrument in the transportation process, the output of the instrument is destroyed, and the instrument should be changed.

C) Remove the faulty thermocouple from the meter, use a multimeter to measure the ohms (R)*1 file, and use the multimeter to measure the two ends of the thermocouple. If the resistance value displayed on the multimeter is large, explain The thermocouple is connected externally and replaced with the same type of thermocouple. Otherwise, there is a positive resistance value, and there is a problem with the output of the instrument. The meter should be changed.

2) According to the wiring diagram of the instrument, the wiring is accurate. If the instrument is energized, the digital tube on the meter displays a negative value, which explains the connection between the thermocouples “+” and “-” connected to the instrument. Only replace it with a new one.

3) Accurate wiring When the instrument is running, the temperature displayed on the digital tube on the meter differs from the temperature measured by practice by 30oC~60oC. Even the difference is even greater, and the index number of the interpreter is wrong with the index number of the thermocouple. According to the correspondence between the temperature (oC) and the millivolt (MV) value of the thermocouple with thermocouple indexing numbers B, S, K, E, etc., the millivolt value (MV) occurs in the same temperature (oC) state. The B index number is the smallest, the S index number is small, the K index number is larger, and the E index number is the largest. It is judged according to this principle.