A thermistor is a common electronic component that is sensitive to temperature. Due thermistor’s high sensitivity, ability to detect subtle temperature changes, wide operating temperature range, it is used for temperature control in air conditioners, microwave ovens, toaster ovens, printers, etc.
The characteristic of the thermistor is that its resistance changes with the change of temperature. The thermistor is divided into positive temperature coefficient thermistor and negative temperature coefficient thermistor according to the different temperature coefficients. The positive temperature coefficient thermistor is abbreviated as PTC. The resistance of the thermistor increases as the temperature rises. The negative temperature coefficient thermistor is referred to as the NTC thermistor, and its resistance decreases with the decrease of the temperature.
Thermistor has an important parameter: B value. The B value is the material constant of the NTC thermistor, which can also be called the thermal index. After the chip of the thermistor is sintered at high temperature, a material with a certain resistivity is formed, which is used to describe the physical properties of the thermistor material. There is only one B value for each formulation and sintering temperature that makes the thermistor, reflecting the change in resistance between the two temperatures.
The B value can be calculated by measuring the resistance value at 25°C and 50°C (or 85°C). The larger the B value is, the faster the resistance value decreases with the increase of temperature, and the higher the sensitivity is, the smaller the B value is, the opposite is true. It should be noted that in actual operation, the B value is not a constant, but increases slightly with the increase of temperature.
The B value of the NTC thermistor is generally between 2000K-6000K, and the size of the B value depends on the application. For products used as temperature measurement, temperature compensation and surge suppression resistance, under the same conditions, it is better to have a larger B value. Because with the change of temperature, the resistance value of the product with a large B value changes more, which means that the thermistor is more sensitive to temperature.
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Post time: Nov-02-2022