Material classification of thermistors

Thermistoris a sensor resistance whose resistance value changes with temperature. According to the temperature coefficient, it can be divided into positive temperature coefficient thermistor and negative temperature coefficient thermistor. The resistance value of the positive temperature coefficient thermistor increases with the increase of temperature, and the resistance value of the negative temperature coefficient thermistor decreases with the increase of temperature. They are both semiconductor devices< Br/>

In general, thermistor materials can be divided into three categories: semiconductors, metals and alloys. The semiconductor thermistor materials are briefly described as follows, including single crystal semiconductors, polycrystalline semiconductors, glass semiconductors, organic semiconductors and metal oxides. They all have very large resistance temperature coefficient and high resistivity, and the sensitivity of sensors made of them is also quite high. According to the resistance temperature coefficient, it can also be divided into negative resistance temperature coefficient materials and positive resistance temperature coefficient materials. In a limited temperature range, the negative resistance temperature coefficient material can reach - 6 * 10-2/℃, and the positive resistance temperature coefficient material can reach - 60 * 10-2/℃ or above. For example, barium argillate ceramic is an ideal semiconductor material with positive resistance and positive temperature coefficient. The above two materials are widely used in temperature measurement, temperature control, temperature supplement, switching circuit, overload protection and time delay, etc., such as the manufacture of thermistor thermometer, thermistor switch and thermistor delay relay error with sub-components

Because thethermistorof this material has an exponential relationship with fluidity, the temperature measurement range is narrow and the uniformity is poor. Metal thermistor materials These materials are widely used in thermal resistance temperature measurement, current limiter and automatic thermostatic heating elements. Such as platinum resistance thermometer, nickel resistance thermometer, copper resistance thermometer, etc. The platinum temperature sensor is applicable to a variety of media (including corrosive media), showing obvious characteristics of high accuracy and high stability. However, the scarcity and high price of platinum limit its wide application. Copper temperature sensors are cheaper, but long-term use in corrosive media will lead to significant changes in static characteristics and resistance values. It is reported that the copper temperature sensor can be used in the temperature range of - 60~180 ℃ in the air medium. However, in order to measure the temperature of - 60~180 ℃ for a long time and 250 ℃ for a short time, nickel temperature sensors have been widely used abroad. Nickel is considered as an ideal material because of its high sensitivity, good repeatability and good stability

Alloy thermistor material is also called thermistor alloy. This alloy has a high resistivity, and its resistance value is very sensitive to the change of temperature. It is a good material for manufacturing temperature sensitive sensors. The performance requirements of thermistor alloys used as temperature sensors are as follows: enough resistivity; The resistance temperature coefficient is high; The linear expansion coefficient is close to the experimental material; The strain sensitivity coefficient is small; When heating and cooling within the working temperature range, the resistance temperature curve shall have good repeatability