How to judge the quality of thermocouple?

What is a thermocouple? Thermocouple is a common temperature measuring element in the temperature measuring surface. It directly measures the temperature and converts the temperature signal into thermoelectric electromotive force signal, which is converted into the temperature of the measured medium through the electrical surface (secondary surface). The appearance of various thermocouples is often very different because of the need, but their basic structure is roughly the same, generally composed of thermal electrode, insulation sleeve protection tube and junction box and other primary parts, generally and flash surface, record surface and electronic regulator matching use. This paper has collected and sorted out some thermocouple related information, and it is expected that this paper will be of great value to readers.

How to judge the quality of thermocouple?

1, visual investigation of the protection tube for corrosion, penetration, leakage, etc.

2. Use a multimeter to measure the connectivity. Assembled thermocouple resistance is generally not greater than 2 Ohms, wire resistance is generally not greater than 50 Ohms, generally greater than 1K can confirm that the thermocouple has been damaged.

3. Use a multimeter to measure the resistance. If the resistance exceeds 100K, it is not good.

4, use multimeter ohm measurement method to measure, adjust the resistance, connect both ends, burn with a lighter. If the multimeter pointer becomes significantly larger or smaller, the description should be good. If the pointer doesn't move, it's broken.

5. Use a multimeter to measure the voltage at both ends in millivolt range. Assuming there is no voltage, it will break.

6, remove the thermocouple from the instrument thermocouple input end, and then short-circuit the instrument thermocouple input end with an arbitrary wire. Switch on the power supply, when the flash value of the digital tube on the top of the surface is about room temperature, indicating that the internal wiring of the thermocouple is open, and the thermocouple of the same type should be replaced. If the condition is still in the above condition, it indicates that the input terminal of the instrument is damaged during transportation and the instrument should be replaced.

7. Remove the thermocouple of the surface of the above shortcomings and replace it with a thermocouple connected with the same indexing surface of normal operation around. After power-on, when the digital tube on the original defect surface flashes the temperature of the heating body, it indicates that the thermocouple is open and replaced with the same type of thermocouple.

8. Remove the defective thermocouple from the surface, measure ohm (R)*1 with a multimeter, and measure both ends of the thermocouple with the two meter rods of the multimeter. Assume that the resistance value flashed by the multimeter is very large, indicating that the internal connection of the thermocouple is open. Replace the same type of thermocouple. Otherwise, there is a certain resistance value, indicating that there is a problem with the surface input, and the surface should be replaced.

9. Correct wiring according to the surface wiring diagram. Assume that after the surface is energized, the nib tube on the surface flashes a negative value, then the thermocouple connection error indicating the surface "+" and "-" connection is indicated. It would be nice to change it again.