When testing the characteristics of a thermistor, the most common tool used is a multimeter. The process typically involves a few key steps that help determine whether the thermistor is functioning properly or not.
The first step is to conduct a room temperature test. It's important that the ambient temperature is close to 25°C for accurate results. To perform this test, you don’t need to use standard test leads. Instead, it’s better to use alligator clips to connect to the two ends of the PTC thermistor.
Once connected, measure the resistance value using the multimeter. Compare this measured value with the nominal resistance specified on the thermistor. If the actual reading is within ±2 ohms of the nominal value, the thermistor is likely in good condition. However, if the difference is significantly larger, it could indicate that the thermistor is damaged or not performing as expected. In such cases, it should no longer be used and should be replaced.
The second step involves a heating test. If the thermistor passes the initial room temperature test, it doesn’t necessarily mean it’s fully functional. To further verify its performance, we can perform a heat test. Place a heat source, such as a soldering iron, near the thermistor and gradually increase the temperature.
As the temperature rises, observe the multimeter reading. A properly functioning thermistor should show a gradual change in resistance as the temperature increases. Once the temperature stabilizes, the resistance value should also stabilize. This indicates that the thermistor is working correctly.
However, if there is no change in the resistance value during heating, it means the thermistor is faulty and cannot be used anymore. In this case, it must be replaced with a new one to ensure proper functionality.
By following these two basic tests—room temperature measurement and heat response—you can effectively evaluate the condition of a thermistor and determine whether it needs to be replaced or not.
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