What is the difference between PTC thermistor and NTC thermistor

时间:2019-06-19 丨 预览:157 人次

Both PTC and NTC are thermistors, which can be divided into many types according to different temperature coefficients. NTC thermistor and PTC thermistor are the two most commonly used types. Although both are thermistors, there are certain differences between NTC thermistors and PTC thermistors.


PTC refers to the thermistor phenomenon or data with a positive temperature coefficient that increases rapidly at a certain temperature, and can be used as a stable temperature sensor. This data is a sintered body with BaTiO3, SrTiO3 or PbTiO3 as the main component, and a small amount of oxides such as Nb, Ta, Bi, Sb, Y, and La are doped to control the valence to make it semi-conducting. Semiconductorized BaTiO3 and other materials are referred to as semiconducting (bulk) porcelain; together with Mn, Fe, Cu, Cr oxides and other additives that increase its positive resistance temperature coefficient, they are formed using general ceramic technology, High-temperature sintering makes semiconducting platinum titanate and its solid solution, so as to obtain positive thermistor data. Its temperature coefficient and Curie point temperature vary with the composition and sintering conditions (especially the cooling temperature).


In addition to being used as a heating element, the PTC thermistor can also play the role of a "switch". It also has three functions of a sensitive element, a heater and a switch, which is called a "thermal switch". After the current passes through the component, the temperature rises, that is, the temperature of the heating element rises. When the temperature exceeds the Curie point, the resistance increases, thereby limiting the current increase, so the current drop causes the temperature of the component to decrease, and the decrease in the resistance value causes the circuit current As the temperature of the component increases, the temperature of the component rises again and again, so it has the function of keeping the temperature at a specific scale, and it also has a switching effect. Using this temperature resistance characteristic as a heating source, heaters, electric irons, drying cabinets, air conditioners, etc. are used as heating elements, and can also have an overheating protection effect on electrical appliances.


NTC refers to the thermistor phenomenon and data with negative temperature coefficient that decreases exponentially with increasing temperature. This data is a semi-conductor ceramics made by manganese, copper, silicon, cobalt, iron, nickel, zinc and other two or more kinds of metal oxides through sufficient mixing, molding, sintering and other processes, which can be made with a negative temperature coefficient. (NTC) thermistor. Its resistivity and data constant vary with the data component share, sintering atmosphere, sintering temperature and structural state. Now the data of non-oxide NTC thermistors represented by silicon carbide, tin selenide, tantalum nitride, etc. are also presented.


NTC thermal semiconductors are mostly oxide ceramics with spinel structure or other structures, which have a negative temperature coefficient, and the resistance value can be approximated as:


Rt = RT * EXP (Bn * (1 / T-1 / T0)


In the formula, RT and RT0 are the resistance value at temperature T and T0 respectively, and Bn is the data constant. The ceramic grain itself changes the resistivity due to the temperature change, which is determined by the characteristics of the semiconductor. The accuracy of the thermometer can reach 0.1 ℃, and the temperature sensing time can be less than 10s. It is not only suitable for the temperature measurement of the granary, but also can be used for temperature measurement in food storage, medicine and health, scientific farming, ocean, deep well, high altitude, glacier, etc.