Thermistors include positive temperature coefficient (PTC) and negative temperature coefficient (NTC) thermistors, and critical temperature thermistors (CTRS).
1.PTC thermistor
The Positive Temperature CoeffiCient (PTC) is a thermistor phenomenon or material that has a positive temperature coefficient and a sharp increase in resistance at a certain temperature. It can be used as a constant temperature sensor. The material is a sintered body with BaTiO3, SrTiO3 or PbTiO3 as the main component, and also adds oxides of Mn, Fe, Cu and Cr that increase the positive resistance temperature coefficient and other additives that play other roles. The material is formed by common ceramic process and sintered at high temperature to make platinum titanate and its solid solution semi-conductive. Thus thermistor materials with positive characteristics are obtained. The temperature coefficient and Curie point temperature vary with the composition and sintering conditions (especially the cooling temperature).
PTC thermistor appeared in the 20th century, PTC thermistor can be used for temperature measurement and control in industry, also used for the temperature detection and regulation of a part of the automobile, but also a large number of civil equipment, such as control of the instant water heater water temperature, air conditioner and cold storage temperature, the use of its own heating for gas analysis and anemometer and other aspects.
PCT thermistor has the function of keeping the temperature in a specific range, and also plays the role of switching. Using this temperature resistance characteristic as a heating source, it can also play the role of overheating protection for electric appliances.
2.NTC thermistor
Negative Temperature CoeffiCient (NTC) refers to a thermistor phenomenon and material that has a negative temperature coefficient because the resistance decreases exponentially as the temperature rises. The material is a semiconducting ceramic made of two or more metal oxides such as manganese, copper, silicon, cobalt, iron, nickel, and zinc, which are fully mixed, formed, and sintered to produce a thermistor with a negative temperature coefficient (NTC).
The development stage of NTC thermistor: from its discovery in the 19th century to its development in the 20th century, it is still being perfected.
The precision of thermistor thermometer can reach 0. 1℃, and the temperature sensing time can be less than 10s. It is not only suitable for granary thermometer, but also can be used in food storage, medicine and health, scientific farming, ocean, deep well, high altitude, glacier temperature measurement.
3.CTR thermistor
Critical Temperature Thermistor CTR (Critical Temperature Resistor) has a negative resistance mutation characteristic, at a certain temperature, the resistance decreases dramatically with the increase of temperature and has a large negative temperature coefficient. The composition material is vanadium, barium, strontium, phosphorus and other elements of the mixed sintered body, is a semi-glassy semiconductor, also known as CTR for glass thermistor. CTR can be used as temperature control alarm and other applications.
Thermistor can also be used as electronic circuit element for instrument circuit temperature compensation and temperature compensation of thermocouple cold end. Automatic gain control can be realized by using the self-heating characteristic of NTC thermistor, and the amplitude stabilization circuit, delay circuit and protection circuit of RC oscillator can be constructed. PTC thermistor is mainly used in electrical equipment overheating protection, contactless relay, constant temperature, automatic gain control, motor start, time delay, color TV automatic demagging, fire alarm and temperature compensation, etc.
Post time: Jan-16-2023