Thermocouple insulation resistance
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For industrial K-type thermocouples, the temperature measured is usually around 360°C. At this temperature, the insulation resistance between the thermocouple wire and the sheath is 1.1 MΩ. Is this value acceptable, and can the thermocouple still be used? Could you, sir, provide some explanation?
Personally, I think as long as the thermoelectric potential is normal, the subsequent measurement unit will work fine. In some cases, the thermocouple core is in direct welded contact with the outer sleeve to eliminate thermal response.
Thermal resistors require insulation, while thermocouples do not; as long as they can function properly, that is sufficient.
Only the outer sleeve can be seen; the internal wire is not visible as it’s welded inside. How can the insulation resistance be measured then? :lol
Are there any regulations or requirements regarding the insulation resistance of thermocouples?
How is the insulation resistance of a thermocouple measured? How to check insulation resistance?
Unwind the wire, and use a 500V megohmmeter to measure the insulation resistance between the core wire and the sleeve. The resistance of a thermistor is infinite at room temperature; it is at least 10 megohms in the range of 100–300 degrees, and at least 2 megohms in the range of 300–500 degrees. The exact value depends on the actual conditions – sometimes a lower value does not affect the measurement, but extremely low values will definitely lead to errors.
No requirements are imposed on thermocouples; even if the hot end touches the protective tube, it does not affect the measurement.
I don’t think it matters; it can be used continued. Since the voltage in the detection circuit is very low, this insulation resistance value is sufficient.
Is it because of the fear that poor insulation could cause electric shock and death? This problem is very serious.
At 360°C, the insulation resistance of the thermocouple is 1.1 MΩ. Such a low value is sufficient for measurement purposes, but could there be any risks associated with this? Unstable? Wait. The thermocouple in our company is inserted to a depth of 5.5 meters and is used in the SIS interlock system; if there are any problems, it could lead to an interlocked shutdown