Introduction to the related functions of the thermistor

1.Protection component

For example, a polymer positive temperature coefficient thermistor (PPTC) is a conductive polymer formed by using a special polymer mixed conductive particle. Under normal ambient temperature, the conductive particles inside the material contain a low-impedance structure, and when the temperature rises. When the temperature is above the transition temperature of the material, the structure of the polymer changes from a crystalline state to an amorphous state, and the conductive particles are separated by an increase in volume, so that the impedance suddenly increases in the current in the circuit, and the temperature of the PPTC thermistor also follows. Ascending, when the temperature rises above the transition temperature (Tt), the sharply increased impedance can surge the current, thereby achieving the purpose of protecting the component.

2. Temperature compensation

Because the resistance value of the negative temperature coefficient thermistor (NTC) can decrease with the rise of temperature, the negative temperature coefficient thermistor is placed in the circuit, and the total resistance of the circuit without the negative temperature coefficient thermistor increases with temperature ( Rc), and with the addition of the negative temperature coefficient thermistor, the total resistance of the circuit, RTotal, does not change significantly with temperature.

3. Level sensor

As the current increases, the heat generated by the NTC thermistor causes the temperature of the component itself to rise and exchange heat with the environment. The liquid level sensor uses the NTC thermistor to dissipate heat in the liquid and air. When the current increases, the NTC thermistor generates Joule heat and then heats up. The heat is conducted to the surrounding medium, and the equilibrium temperature will follow the medium. Different from type to item. Using this method, the NTC thermistor can be detected in the liquid or in the air to activate the warning light at the right time.