The so-called thermistor is a resistor that is extremely sensitive to temperature. When the temperature of this resistor changes, its resistance value will also change accordingly.
At present, there are many kinds of thermistors in the market, and there are many classification methods:
According to its structure and shape, it can be roughly divided into spherical, rod-shaped, tubular, disc-shaped, circular and so on.
According to the different heating modes, it can be roughly divided into direct heating thermistors and side heating thermistors.
According to the working temperature range, it can be divided into normal temperature, high temperature and ultra-low temperature thermistors.
According to the temperature coefficient, it can be divided into positive temperature coefficient thermistors and negative temperature coefficient thermistors. At present, the most widely used thermistors are negative temperature coefficient thermistors, which can be divided into temperature measuring type, voltage stabilizing type and common type.
Generally speaking, the nominal value of the thermistor refers to the resistance value when the ambient temperature is 25 ℃. When using a multimeter to measure its resistance value, its resistance value may not be consistent with the nominal resistance value. For example, the positive temperature coefficient thermistor is also called PTC thermistor. When the temperature of this kind of resistor rises, the resistance value will also increase. Meanwhile, the change of resistance value is in direct proportion to the change of temperature. However, when the temperature of the resistor exceeds a fixed value, its resistance value will increase sharply. Once it increases to the maximum value, the resistance value will gradually decrease with the increase of temperature.