Basic Operation
Assuming, as a first-order approximation, that the relationship between resistance and temperature is linear, then:
where
- = change in resistance
- = change in temperature
- = first-order temperature coefficient of resistance
Thermistors can be classified into two types, depending on the sign of . If is positive, the resistance increases with increasing temperature, and the device is called a positive temperature coefficient (PTC) thermistor, or posistor. If is negative, the resistance decreases with increasing temperature, and the device is called a negative temperature coefficient (NTC) thermistor. Resistors that are not thermistors are designed to have a as close to zero as possible, so that their resistance remains nearly constant over a wide temperature range.
Instead of the temperature coefficient k, sometimes the temperature coefficient of resistance (alpha sub T) is used. It is defined as
This coefficient should not be confused with the parameter below.
Read more about this topic: Thermistor
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