How to detect fault in a thermistor?
11 Jul, 2025
(1) Visual Inspection
First, observe the thermistor's exterior. Ensure the potentiometer or thermistor has clear markings, with no corrosion on solder tabs or pins. The rotating shaft should turn smoothly with appropriate tightness, and there should be no mechanical noise or jitter during rotation.
(2) Check for Loose Connections
Gently shake the solder tabs or pins of the potentiometer or thermistor. There should be no looseness detected.
(3) Resistance Measurement
- Set the multimeter to the appropriate resistance range and perform ohm zero adjustment.
- Connect the multimeter probes (ignoring polarity) to the thermistor's two terminals. Measure the actual resistance value.
- Compare the measured value with the thermistor's nominal value:
- If the pointer does not move, the internal resistor is open-circuited (damaged).
- A significant deviation from the nominal value indicates a fault.
(4) Contact Point Test
- Connect one probe to the center pin (linked to the internal moving contact) and the other to any other terminal.
- Slowly rotate the shaft. The meter needle should move smoothly and correspondingly.
- Jumping or dropping of the needle suggests poor contact between the moving contact and resistor element.
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