Which is not the important characteristics of thermistors that make them extremely useful in measurement and control applications ?

Thermistor:

It is a resistance thermometer or a resistor whose resistance depends on temperature.

Thermistor = Thermal + Resistor

Resistance-Temperature Characteristics:

\({R_{{T_1}}} = {R_{{T_2}}}{e^{\beta \left( {\frac{1}{{{T_1}}} - \frac{1}{{{T_2}}}} \right)}}\)

R_T1 = Resistance at T₁ °C

R_T2 = Resistance at T₂ °C

β = constant depending on the material

Observation: When the temperature increases, the resistance is decreased due to the negative temperature coefficient.

Voltage-current characteristics:

It first follow Ohm’s law, i.e.

V ∝ I

After a certain large current limit, i.e. at larger applied voltage, enough heat is produced, to make the thermistor temperature rise above the ambient temperature, and its resistance then decreases, i.e. with a further increase in current, the resistance decreases.

Current-time characteristics:

It indicates the time delay of the applied voltage.

At first, the current increases with time. It then reaches a maximum current and started to become constant afterward.

The power time characteristics is not an important thermistor characteristic.