Precautions when measuring the resistance parameters of NTC

The method of measuring NTC thermistor with a multimeter is the same as the method of measuring ordinary fixed resistance, that is, the actual value of Rt can be directly measured by selecting an appropriate electrical barrier according to the nominal resistance of the NTC thermistor. But because NTC thermistor is very sensitive to temperature, the following points should be paid attention to when testing:

  (1) It can be known from the definition of the nominal resistance value Rt that this value is measured by the manufacturer when the ambient temperature is 25℃. Therefore, 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 must not exceed the specified value, so as to avoid the measurement error caused by the current heating effect. For example: epoxy packaged NTC thermistor, its rated power is generally below 50mW, and the measured power P1 = 0.2mW. Assuming that the nominal resistance value Rt is 1kΩ, the test current:

  Obviously, it is more appropriate to use the R×1k gear. The full-scale current Im of this gear is usually tens to 100 tens of microamperes. For example, the R×1k block of the multi-purpose 500 multimeter has Im=150uA, which is very close to 141uA.

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