How to determine the quality of a thermal resistor
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It is a cryogenic container designed for use at temperatures of -143°C; the insulation layer inside contains perlite. There are 8 temperature monitoring points in the insulation layer at the bottom of the container. Under normal operating conditions, the temperatures recorded were all above -20°C. However, one of these points gradually dropped to -70°C during use. By implementing ventilation measures at the bottom, the temperature at that point rose to -60°C. Since it’s not possible to determine whether the thermistor is functioning properly, removing it to test it directly would be too costly. Therefore, I hope someone experienced can suggest a solution.
You can determine it by measuring the resistance value of the faulty resistor with an ohmmeter.
There can only be two possibilities: either the actual temperature is indeed that much, or there is a problem with the thermal resistor. First, assume that the thermal resistor reflects the actual temperature; check the equipment or the production process to see if there are any issues. Once it is confirmed that there are no problems with the equipment or process, the only option left is to replace the thermal resistor.