A thermistor is a component of a semiconductor ceramic working body that is very sensitive to temperature.Compared with the commonly used metal resistance,It has a much larger resistance temperature coefficient value.According to the different temperature coefficient of resistance.
Thermistors can be divided into three categories:
  1. Positive temperature coefficient thermistor;
2. Critical resistance temperature coefficient thermistor;
3. Common negative temperature coefficient thermistor.The first two types of resistance to sudden changes in the region,Narrow temperature range,It is suitable for use in a specific temperature range as a control and alarm sensor.
The third category in the field of temperature measurement is widely used,A thermistor as the temperature sensor has a material saving,Low cost, small size, simple structure, the absolute value of the temperature coefficient of resistance and other advantages,It can be simple, sensitive measure small changes in temperature.
 
The so-called resistance temperature coefficient (α),Refers to the zero load resistance change rate at 1 ° C (K) at any temperature.Resistance temperature coefficient (α) and the relationship between the value of B,Differential Equation 1 can be obtained.


Here before α minus (-),Indicates that the zero load resistance decreases when the temperature rises.
Heat dissipation coefficient (JIS-C2570)
The heat dissipation factor (δ) refers to the heat balance
The power required for the thermistor element to raise its temperature by 1 ° C by its own heat.

In the heat balance state,Thermistor temperature T1,The relationship between the ambient temperature T2 and the power consumption P is shown in the following equation.


The catalog value is typical for the following measurement conditions.
(1) 25 ° C in still air.
(2) axial pin, the lead-pin type in the factory state to determine.