How to test the quality of thermistors.Infrared Body Sensing Module

　　There are two types of thermistors, NTC (Negative temperature coefficient) and PTC (positive temperature coefficient type). As its name suggests, the resistance of NTC thermistors decreases with temperature, while the resistance of PTC thermistors increases with temperature. The quality of PTC and NTC thermistors can be roughly checked using a multimeter.

　　Keep the multimeter in resistance mode. Connect the multimeter terminals to the thermistor leads, where the positive and negative poles of the terminals can be ignored. Then move the heated soldering iron head onto the thermistor to heat the thermistor. Pay attention that the electric soldering iron is only close and cannot touch the thermistor, otherwise it may damage the thermistor. During the process of temperature rise, it can be seen that the multimeter reading increases or decreases smoothly (depending on whether the measured thermistor is PTC or NTC). If the reading increases or decreases normally, it indicates that the performance of this thermistor is normal and there has been no malfunction.

　　For faults in thermistors, the following observations can be made:

　　1. The change in resistance value will not be smooth, and there will be no change, so the resistance can have a fault.

　　2. If the instrument reading remains zero and does not change, it may be due to a short circuit in the thermistor wire.

　　3. For open thermistors, the instrument reading is always infinite.

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