Precautions for detecting the thermistor

When testing, use the multimeter ohm file (depending on the nominal resistance value to determine the gear position, generally R × 1 block), the specific can be divided into two steps: first room temperature detection (indoor temperature is close to 25 ° C), with the alligator clip instead of the test pen respectively The actual value of the two pins of the PTC thermistor is measured and compared with the nominal resistance. The difference between the two is within ±2 Ω. If the actual resistance is too different from the nominal resistance, it indicates poor performance or damage.

Secondly, the heating test, on the basis of the normal temperature test, can be carried out in the second step test - heating detection, a heat source (such as a soldering iron) is heated close to the thermistor, and the universal representation number is observed. It is seen that the universal display changes with the increase of temperature, which indicates that the resistance value is gradually changing (the negative temperature coefficient thermistor NTC resistance value will become smaller, and the positive temperature coefficient thermistor PTC resistance value will become larger) When the resistance value changes to a certain value, the display data will gradually stabilize, indicating that the thermistor is normal. If the resistance value does not change, the performance is deteriorated and cannot be used.

The notes for detecting the thermistor are as follows:

1.Rt is measured by the manufacturer at an ambient temperature of 25 ° C, so when measuring Rt with a multimeter, it should also be carried out when the ambient temperature is close to 25 ° C to ensure the reliability of the test;

2. The measured power shall not exceed the specified value to avoid the measurement error caused by the current thermal effect;

3. Pay attention to the correct operation. When testing, do not hold the thermistor body by hand to prevent the body temperature from affecting the test;

4. Be careful not to get the heat source and the PTC thermistor too close or directly in contact with the thermistor to prevent it from being burnt.