THERMISTOR

Thermistors are semiconductors made of ceramic materials which have a high negative temperature coefficient of resistance. They can be small in size (e.g. 0.5 mm in diameter) and have relatively large sensitivity to temperature changes (-3% to -5% change per [d]C), and have good long-term stability. Change of resistance is not linear with temperature but when employed in a bridge circuit good linearity can be achieved. The current through thermistors must be small to prevent electrical heating, and they are usually encapsulated in glass. Some electrical clinical thermometers use thermistors, often with a disposable sheath.

Thermistors are also used in breathing rate meters in which the device is taped to be in the airstream in the mouth (at the lips) or in the nose.

Content and Design Copyright 2000 Dr. Malcolm C Brown.  See Title Page for more details