Main Applicative Characteristics of Thermistor

Large temperature coefficient allows for sensitivity, and replying speed is fast, allowing rapid reaction to temperature change.

Does not require cold junction or compensating wire.

High resistance allows overriding of wire resistance enabling remote control and management.

The relational characteristic between temperature given to Thermistor itself and the no-load resistance value of the Thermistor is closely connected and may be expressed as the following.

R @ T = RO @ TO EXP β (1 / T-1 / TO)

R @ T : resistance value at absolute temperature T(K)

R @TO : resistance value at absolute temperature TO (K)

β : Thermistor B constant

T, TO : absolute temperature (K = ℃ +273.15)

Within a very small current range, self-heating of Thermistor is small, thus is expressed linearly in accordance of ohm rule, the voltage in proportion to the current. (E=IR) However, when the current increases, the voltage acquires the highest value at a certin current, and even if the current increases further, the voltage actually starts to decrease. In other words, dE / dI continues to decrease.

For reduction in resistance, it does not immediately decrease even when current sufficient for Thermistor to heat up is added, and when the Thermistor excits from the equivalent circuit, there is always a time delay before it arrives at balanced operation status. Such characterstic depends on heat dissipation constant of Thermistor, quanity of heat and circuit composition.

Main Characteristics and Applied Areas of Thermistor