CSLB C-46 Solar ContractorSolar Thermal System InstallationEasy
A solar thermal system installer is using a multimeter to check the resistance of a thermistor used as a collector temperature sensor. The multimeter reads 10,000 ohms at 25°C. If the collector temperature increases, how should the resistance reading change for a Negative Temperature Coefficient (NTC) thermistor?
- ARemain constant
- BIncrease slightly
- CDecrease significantly
- DIncrease significantly
Show answer & explanationAnswer & explanation
Correct answer: C. Decrease significantly
An NTC (Negative Temperature Coefficient) thermistor's resistance decreases as its temperature increases. This inverse relationship is fundamental to its operation as a temperature sensor.
Why the other options are wrong
- A. This would indicate a faulty sensor or a non-thermistor component.
- B. While the change might be slight depending on the temperature, the direction of change for an NTC is always a decrease.
- D. This describes a Positive Temperature Coefficient (PTC) thermistor.
NTC Thermistor Behavior
A type of thermistor whose electrical resistance decreases as its temperature increases.
- Commonly used as temperature sensors in solar thermal controllers.
- Provides an inversely proportional relationship between resistance and temperature.
- Essential for accurate temperature measurement and system control.
Memory trick: NTC: Negative temp means resistance drops, when the heat just pops!