What are NTC temperature sensors?

NTC temperature sensors (negative temperature coefficient) are resistors whose electrical resistance decreases significantly as the temperature rises. They are usually made of semiconductor materials such as metal oxides, are widely used and inexpensive. Typical NTCs have, for example, 10 kΩ at 25 °C and are described by the B value (characteristic number for the steepness of the characteristic curve). One disadvantage is their limited interchangeability; when selecting an NTC, not only the nominal resistance but also the B value must be taken into account.