When testing, use a multimeter ohm gear (depending on the nominal resistance value to determine the gear, generally R × 1 gear), which can be divided into two steps: first, the normal temperature detection (the indoor temperature is close to 25 ℃), use crocodile clips instead The two pins of the PTC thermistor are measured by the test leads and their actual resistance values ​​are measured and compared with the nominal resistance values. The difference between the two is within ± 2Ω is normal. If the actual resistance value is too different from the nominal resistance value, it means that its performance is poor or damaged. Secondly, the heating test, on the basis of normal room temperature test, you can perform the second step test-heating test, heat a heat source (such as an electric soldering iron) close to the thermistor, and observe the universal expression number, such as Seeing that the universal indicator changes with increasing temperature, this 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 displayed data will gradually stabilize, indicating that the thermistor is normal. If the resistance value does not change, it means that its performance has deteriorated and it cannot be used.   

The following points should be noted when testing:   

(1) Rt is measured by the manufacturer when the ambient temperature is 25 ℃, so when measuring Rt with a multimeter, it should also be performed when the ambient temperature is close to 25 ℃ to ensure the credibility of the test.   

(2) The measured power must not exceed the specified value to avoid measurement errors caused by current thermal effects.   

(3) Pay attention to correct operation. During the test, do not pinch the thermistor body with your hand to prevent the body temperature from affecting the test.   

(4) Be careful not to put the heat source close to the PTC thermistor or directly contact the thermistor to prevent it from being burnt.