Applications of NTC Thermistors in Sensors

1. Brief Introduction

NTC (Negative Temperature Coefficient) thermistor is a type of semiconductor resistor whose resistance decreases significantly as the temperature rises. With high temperature sensitivity, small size, fast thermal response and low cost, NTC thermistors are widely used in various sensors for temperature detection, parameter compensation and overheat protection.

2. Working Principle

The resistance value of an NTC thermistor changes continuously with ambient or measured temperature. Through a voltage divider circuit, the resistance variation is converted into voltage signal. The microcontroller collects analog signals and calculates the accurate temperature to realize sensing detection, automatic control and safety protection.

3. Main Applications in Sensors

(1) Direct Temperature Sensors

This is the most primary application. NTC thermistors act as temperature probes to measure temperature directly.

●Household appliances: Air conditioners, refrigerators, water heaters, washing machines detect internal and ambient temperature to achieve automatic temperature control.

●Automotive electronics: They are applied in water temperature sensors, intake air temperature sensors and oil temperature sensors of vehicles.

●New energy batteries: NTC thermistors monitor lithium battery temperature in electric vehicles, power banks and energy storage systems, preventing overheating damage.

●Industrial equipment: They are used in constant temperature devices, cold chain monitoring and medical instruments for temperature collection.

(2) Indirect Physical Quantity Sensors

Based on thermal dissipation principle, NTC can detect other physical parameters besides temperature.

●Air flow & wind speed sensors: Airflow takes away heat from the heated NTC thermistor. Faster airflow leads to greater resistance change, so wind speed and flow rate can be measured.

●Liquid level sensors: Liquid and air have different heat dissipation capabilities. The resistance difference of NTC can judge liquid level and detect water shortage.

(3) Temperature Compensation for Other Sensors

Many sensors such as pressure sensors, Hall sensors, photoelectric sensors and gas sensors have signal drift caused by temperature changes. NTC thermistors are connected in series or parallel in circuits to compensate temperature drift, improve measurement accuracy and working stability.

(4) Overheat Protection Sensors

NTC thermistors are attached to power devices, transformers, motors and circuit boards to monitor temperature in real time. When temperature exceeds the safe threshold, the circuit will cut off power, reduce power or stop working to avoid device burnout and safety accidents.

4. Advantages

1)Extremely high temperature sensitivity, much higher than metal thermal resistors.

2)Compact structure, available in chip and probe types, suitable for narrow space.

3)Fast thermal response speed.

4)Low cost and suitable for mass production.

5)Simple peripheral circuits and easy signal acquisition.

5. Disadvantages

1)Obvious nonlinear relationship between resistance and temperature, requiring software calibration and lookup table algorithm.

2)Limited temperature measurement range (generally -50℃ to 150℃).

3)Long-term high-temperature operation will cause aging and slight resistance drift.