What are thermistors?

Thermistor, the word created by a combination of thermal with resistor refers to a device whose electrical resistance or the ability to perform electricity is controlled by temperature. Thermistors come in two varieties; NTC, negative thermal coefficient and PTC, positive thermal coefficient, sometimes called positives. They are most often made of metal oxides such as manganese, cobalt, nickel and copper. Metals are oxidized by a chemical reaction, grounded to fine powder, then compressed and subjected to very high heat. Some NTC thermists are crystallized from semiconductor material such as silicon and germanium. NTC thermistors are used to use it to protect circuits from the increase in electric flow that accompanies the start. Since NTC resistors change gradually with temperature, they are also used as a temperature measurement device. They are generally produced by introducing a small amount of semiconductive material into polycrystalline ceramics. When the temperature reaches a critical point, the semiconductor material forms a barrierIt rises very quickly in the flow of electricity and resistance. Unlike gradual changes in NTC thermistors, PTC works more like on-off switches. The temperature at which this occurs can be changed by adjusting the composition of the thermistor.

Another type of PTC thermistor consists of slices of plastic with carbon grains built into it. When the plastic is cold, the carbon grains are close enough to each other to create a conductive path. The plastic expands as it heats up; At a certain temperature, it will be extended to put the carbon grains and break the conductive path.

This on-off behavior of PTC thermistors is useful in situations where the device can be damaged by easily defined events. For example, they can be used to protect windings in transformers and electric motors from excessive heat.