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What is a thermocouple? Thermocouple is a temperature measuring element commonly used in temperature measuring instruments. It directly measures the temperature, converts the temperature signal into a thermoelectromotive force signal, and converts it into the temperature of the measured medium through an electrical instrument (secondary instrument). The shape of various thermocouples is often very different due to needs, but their basic structure is roughly the same, usually composed of main parts such as thermode, insulating sleeve protection tube and junction box, usually with display instruments, recording instruments and electronic adjustment. used in conjunction with the device. This article has collected and sorted out some related information about thermocouples, and I hope this article can be of great reference value to readers.
How to judge the quality of thermocouple?
1. Visually observe whether the protection tube is corroded, penetrated, or leaked.
2. Use a multimeter to measure continuity. The assembled thermocouple resistance is generally not greater than 2 ohms, the network cable resistance is generally not greater than 50 ohms, and generally greater than 1K to determine that the thermocouple has been damaged.
3. Use a multimeter to measure the resistance value, resistance over 100K is not good.
4. Measure with a multimeter ohm measurement method, adjust the resistance, connect both ends, and burn it with a lighter. If the pointer of the multimeter is noticeably larger or smaller, it should be fine. If the pointer doesn't move, it's broken.
5. Use a multimeter to measure the voltage at both ends within the millivolt range. If there is no voltage, it will be broken.
6. Remove the thermocouple from the thermocouple input end of the instrument, and then use any wire to short-circuit the thermocouple input end of the instrument. Turn on the power, when the digital tube on the top of the meter displays about room temperature, it means that the internal wiring of the thermocouple is open, and the thermocouple of the same type should be replaced. If it is still in the above state, the input terminal of the instrument has been damaged during transportation, and the instrument should be replaced.
7. Remove the thermocouple of the above faulty instrument and replace it with the thermocouple connected to the similar indexing instrument that is running normally next to it. After the power is turned on, when the digital tube on the original faulty instrument displays the temperature of the heating body, it means that the thermocouple wiring is open, and the thermocouple of the same type should be replaced.
8. Remove the faulty thermocouple from the meter, measure ohms (R)*1 with a multimeter, and measure both ends of the thermocouple with the two bars of the multimeter. If the resistance value displayed by the multimeter is large, it indicates that the thermocouple is internally connected open circuit. Replace with the same type of thermocouple. Otherwise, there is a certain resistance value, indicating that there is a problem with the input end of the instrument, and the instrument should be replaced.
9. The wiring is correct according to the wiring diagram of the instrument. If the digital tube on the meter displays a negative value after the meter is powered on, it means that the thermocouples connected to the "+" and "-" of the meter are connected incorrectly. Just change it again.
