In industry and agriculture manufacture, national defense, scientific research and office equipment automation fields, temperature is a very critical data. Temperature sensor, i.e. thermistor is a kind of sensor with repeatability and regularity. Among all the temperature sensitive components, thermistor holds a very important position, accounting for 40% of the total temperature sensitive components. According to the characteristics of resistance change with changes in temperature, there are two types of thermistor: NTC thermistor and PTC thermistor. The former resistance decreases when the temperature rises, while the latter resistance increases when the temperature rises. We'd like to focus on
NTC thermistor.
I. R&D for NTC thermistor
Common NTC thermistor is made up of 2~4 transition metal oxides like Mn-Co-Ni-Fe-Cu, with ceramic sintering process. The characteristics of the thermistor is closely related to the ratio of the metal oxides, sintering conditions, and annealing conditions. One of the most important characteristics of NTC material is that resistivity ρ and B value remain the same in a quite wide range, which guarantees the consistency of products. However, when we select suitable material, NTC material is affected by material stability, sintering, consistency, thermal expansivity of the material and auxiliary material, and the cost. In order to improve the stability and working temperature of NTC thermistor, add chromium hemitrioxide, zirconium oxide, aluminium oxide or SiC into transition metal oxide to control the resistivity ρ and B value.
