Non-linear sensors are made of semi-conducting materials, usually metal oxides. The change in resistance, depending on temperature, is strongly non-linear. This variation is due to equations related to sensor manufacture’s used material.
Among non-linear sensors, the most common are Thermally Sensitive Resistors (Thermistor), among which there are Negative Temperature Coefficient NTC and Positive Temperature Coefficient PTC.
Non-linear temperature sensors are used in industries which requires even the minimal temperature variations, being the temperature measuring range generally reduced. Typical examples are industrial related to air conditioning systems, refrigeration, heating systems, control of chemical or food processes.