How To Check A Thermistor When It Goes Wrong

Thermistor is a kind of resistor with nonlinear volt-ampere characteristics that is sensitive to ambient temperature changes. Its resistance value is related to temperature, and the resistance value of thermistor varies greatly within a relatively small temperature range. So how to judge whether there is a problem with the thermistor?

When checking the thermistor, we first check the appearance of the thermistor.

1. The appearance of a normal thermistor should be intact, with clear printing on the shell, no cracks or expansion of the shell, and no rust on the pins. If the surface of the thermistor has cracks or expansion of the shell, unclear printing, rust on the pins, etc., it means that the thermistor has quality problems.

2. Use the ohm file of the multimeter to check. When checking the thermistor, set the resistance of the multimeter to an appropriate range according to the nominal resistance of the thermistor to perform ohm zero adjustment. Check at room temperature (about 25°C), and use two test leads to connect the two terminals of the thermistor respectively. Measure the resistance of the terminal pin. Under normal circumstances, the measured resistance value should be close to the nominal resistance value of the thermistor (the difference between the two is within ±2Ω, which is normal); if the measured resistance value is far from the nominal value, it means that the thermistor is with poor performance or damaged.

3. Heating inspection: further test under normal temperature test conditions – heating inspection. Place a heat source such as a hair dryer close to the thermistor, and observe whether the resistance of the multimeter pointer increases or decreases with the increase of temperature . If the resistance value of the multimeter changes with the increase of temperature, it means that the thermistor is normal; if the resistance value does not change, it means that its performance is deteriorated and cannot be used any more.

When the thermistor has a problem, it should be replaced with a branded and high-quality thermistor of the same model and specification as soon as possible to ensure the normal use of the electrical appliance.

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