What material is the thermal resistance made of?

Classification of thermistor materials

Heat-sensitive materials can generally be divided into three categories: semiconductor, metal and alloy, which are briefly described as follows.

Semiconductor thermistor material

This material includes single crystal semiconductor, polycrystalline semiconductor, glass semiconductor, organic semiconductor and metal oxide. They all have very large temperature coefficient of resistance and high turtle resistance, and the sensitivity of sensors made of them is also quite high. According to the temperature coefficient of resistance, it can also be divided into negative temperature coefficient materials and positive temperature coefficient materials. In a limited temperature range, the negative temperature coefficient material A can reach -6* 10-2/℃, and the positive temperature coefficient material A can reach -60* 10-2/℃. For example, drinking barium ceramics is an ideal semiconductor material with a positive temperature coefficient of resistance. These two materials are widely used in temperature measurement, temperature control, temperature compensation, switching circuit, overload protection and delay, such as thermistor thermometer, thermistor switch and thermistor thermometer, thermistor switch and thermistor time delay relay fault.

Because of the exponential relationship between resistance and fluidity, this kind of material has a narrow temperature measurement range and poor uniformity.

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Metal thermistor material

This kind of material is widely used as thermal resistance temperature measurement, current limiter and automatic constant temperature heating element. Such as platinum resistance thermometer, nickel resistance thermometer and copper resistance thermometer. Among them, the platinum side temperature sensor shows obvious characteristics of high accuracy and stability in various media (including corrosive media). However, due to the scarcity and high price of platinum, their wide application is limited. Copper temperature sensor is cheap, but long-term use in corrosive media will cause obvious changes in static characteristics and resistance. Recently, it has been reported that the copper temperature sensor can be used in the temperature range of -60~ 180℃ in air. However, in order to measure the temperature of -60~ 180℃ for a long time and 250℃ for a short time, nickel temperature sensor is widely used abroad. Nickel is considered as an ideal material because of its high sensitivity, satisfactory repeatability and stability.

Alloy thermistor material

Alloy thermistor materials are also called thermistor alloys. This alloy has high resistivity, and its resistance value is very sensitive to temperature change, so it is a good material for manufacturing temperature-sensitive sensors. As a temperature-sensitive sensor, thermistor alloy has the following performance requirements: (1) enough resistivity; (2) Very high temperature coefficient of resistance; (3) The linear expansion coefficient is close to the experimental material; (4) The strain sensitivity coefficient is small; (5) When heating and cooling in the working temperature range, the resistance temperature curve should have good repeatability.