What applications do NTC thermistors have?
Categories: Industry News
2025-01-02
NTC is usually a semiconductor electronic ceramic with a structure close to theoretical density (4.8g/cm3), made from two or more high-purity metal oxide materials such as Mn, Co, Ni, and Fe through mixing, molding, and sintering.
NTC thermistors are semiconductor resistors whose resistance changes in the opposite trend with temperature, with a very high rate of change.
1. Temperature sensors and nonlinear correction
NTC thermistors are widely used temperature sensors in the industrial temperature measurement field.
The temperature measurement range of thermistors can reach-100℃ ~ 500℃, with a sensitivity of up to -44000 ppm/℃ (at 25℃). Their actual usage size is very flexible, with diameters as small as 0.01 inches or even smaller, and the maximum size is almost unlimited. The rated room temperature resistance depends on its semiconductor material, size, shape, and electrode contact area. Thick and narrow thermistors have relatively high resistance, while thin and wide thermistors have relatively low resistance.
2. Surge protection
To avoid the instantaneous surge current generated when the circuit is turned on, a powerNTC thermistor is usually connected in series. This effectively resists the surge current at startup. After the surge current is resisted, due to the continuous effect of the current, the resistance value of the NTC thermistor will drop to a very small value, resulting in very low power consumption that can be ignored, without affecting the normal operation of the circuit.
Therefore, in small and medium-sized power circuits, the method of using powerNTC thermistors to resist surge currents is widely used. Maximum steady-state current: refers to the maximum continuous current that the thermistor can withstand at 25℃. B value: the thermal coefficient, which is the ratio of the natural logarithm difference of zero power resistance values at two temperatures to the difference of the reciprocals of the two temperatures. The temperature characteristic formula of the thermistor is: the larger the B value, the smaller the residual resistance, and the smaller the working temperature rise.
Thermal time constant: the time required for the resistor's temperature to change from the initial temperature to 63.2% of the final temperature when the ambient temperature suddenly changes at zero power.
The larger the product of the total thermal time constant and the dissipation coefficient of the thermistor, the greater the thermal capacity of the thermistor, and the stronger the resistance to surge currents. The working temperature rise is smaller.
From the above, it can be seen thatthe resistance value of NTC thermistors is very sensitive to temperature, so the characteristics of NTC thermistors can be flexibly applied in practice. To prevent surge current from impacting the circuit, power NTC thermistors can be selected, or temperature-sensitive NTC thermistors can be chosen for temperature compensation or temperature detection.
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2025/01/02
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