What is a common nominal thermistor value and its temperature?

• A. 1000Ω at 70°F.
• B. 10kΩ at 25°C.
• C. 100Ω at 0°C.
• D. 470Ω at 50°F.

Answer: (A)

Thermistors have a resistance that changes with temperature, and their “nominal” value is the resistance at a chosen reference temperature. For good readability in common control circuits, designers pick a reference temperature near typical room conditions and a resistance that isn’t too high or too low. A 1 kΩ thermistor at about 70°F (roughly 21°C) fits that idea well: it sits in a practical range for voltage-divider circuits powered from standard supplies, so the sensor signal changes appreciably with small temperature shifts and can be read accurately by common ADCs. The 1 kΩ value also keeps self-heating modest and the bias currents reasonable.

Other options use different reference temps or much higher/lower nominal resistances, which can reduce sensitivity in typical indoor temperature ranges or complicate the readout design. The choice of 1 kΩ at around room temperature is a traditional, widely convenient pairing for many instrumentation and lab practice scenarios.