物理溫度計

Thermistor thermometers (熱敏電阻溫度計) use thermistors (熱敏電阻) to measure temperature. A thermistor is a semiconductor device with an electrical resistance that is proportional to temperature.

There are two types of thermistors. They are PTC, which stands for Positive Temperature Coefficient of Resistance, and NTC, which stands for Negative Temperature Coefficient of Resistance. NTCs are the most common types of thermistors. They have temperatures that vary inversely with their resistance, so that when the temperature increases, the resistance decreases; and when the temperature decreases, the resistance increases
.
The following is a diagram showing a thermistor thermometer circuit:


圖片參考：https://s.yimg.com/rk/HA00458726/o/906590363.jpg

熱敏電阻溫度計要用電源，不算物理溫度計，普通水銀或酒精溫度計才是，熱敏電阻利用溫度改變電阻值，從而改變運算放大器輸入電壓差，輸出電流至數位計顯示溫度。