Thermistors

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Thermistors
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• A thermistor is another special type of resistor.
  Its resistance changes as its temperature
  changes.
• When the temperature of the thermistor is low,
  its resistance is high. This is because a
  thermistor is made of a material which does not
  conduct electricity well at low temperatures. The
  outer electrons are loosely bound to the atoms
  and are not free to flow through the thermistor.
• As the temperature increases, more outer
  electrons gain enough energy to break free from
  atoms. The electrons are then free to flow
  through the thermistor.

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• This graph shows the thermistors resistance
  against temperature.
• Remember, the resistance of a thermistor
  decreases as the temperature increases.

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• This change in resistance according to their
  temperature means that thermistors can be used as
  temperature sensors.
• For example, they can be used to warn drivers
  when the car engine is overheating.

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• Most thermistors have a useful working range of
  90 C to 200 C.