How to Test Thermistor Quality Using a Multimeter
When performing the test, use the ohm range of the multimeter. The operation consists of two steps: First, conduct the room-temperature test. Use alligator clips instead of test leads to clamp the two pins of the PTC thermistor respectively and measure its actual resistance value. Compare this reading with the nominal resistance value. A deviation within ±2Ω indicates normal performance. If the difference between the measured resistance and nominal resistance is too large, the component is defective or damaged.
Second, perform the heating test. Proceed to the second step only if the room-temperature test passes. Bring a heat source close to the thermistor to heat it and observe the multimeter reading. If the reading changes as the temperature rises, the resistance value is varying gradually. The displayed value will stabilize once the resistance reaches a certain level, which means the thermistor works normally. If the resistance remains unchanged, its performance has deteriorated and it cannot be used anymore.
Like most resistance measurement methods with a multimeter, when using an analog multimeter to check the quality of a PTC thermistor, set the meter to the R×1 range. The operation also has two steps. For the room-temperature test, touch the two test leads to the two pins of the PTC thermistor to measure its actual resistance and compare it with the nominal value. A deviation within ±2Ω is acceptable. If the discrepancy is excessive, the thermistor is faulty or damaged.
The heating test for the thermistor is carried out after a successful room-temperature test. If the thermistor passes the resistance check described above, proceed with the heating test. Place a heat source near the PTC thermistor to heat it, and monitor whether its resistance increases with rising temperature using the multimeter. If yes, the thermistor is functional; if the resistance shows no change, its performance is poor and it must be discarded. Note: Do not place the heat source too close to or in direct contact with the PTC thermistor to avoid burning it out.
