Thermistor use precautions

The following items need to be taken when using the thermistor:

(1) Self-heating problem

Since the thermistor is a resistor, a certain amount of heat is generated when current flows through it, so the circuit designer should ensure that the series resistor is large enough to prevent the thermistor from self-heating, otherwise the system measures thermal The heat emitted by the resistor, not the temperature of the surrounding environment.

(2) Thermal runaway phenomenon

For example, when NTC is used, the resistance decreases with temperature, which will increase the current flowing through NTC. At this time, the power loss of NTC will increase the power loss by a factor of squared. When the power loss increases, the thermal effect will increase. As a result, the temperature rises, causing the resistance of the NTC to drop again, and the current is then increased again. This cycle is burned out by exceeding the wattage of the NTC load.

(3) Cumulative error

The thermistor resistance changes with temperature. For accuracy, design the circuit to pay attention to the accuracy of the component, including the resistor, reference voltage and thermistor itself, carefully calculate the cumulative error of all components to match the accuracy of the thermistor.

(4) Different reaction speeds

Different types of thermistors vary in temperature due to different temperatures, so different types of thermistors must be selected for different applications.