Thermal Time Constant

Definition - What does Thermal Time Constant mean?

Thermal Time Constant is a measurement of the time which a thermistor takes to respond when the change of 63.2% of the total difference between the final and the initial body temperature is administered when a body is subjected to a convective warming or cooling system.Thermal Time Constant is one of the examples of Time Constant. For any thermal systems, time constant features a lumped capacity analysis method which is used when a body warms or cools uniformly under the influence of convective warming or cooling system.

Petropedia explains Thermal Time Constant

The medium usually affects thermal time constant measurement. If the thermal time constant is measured in moving air, then it will be less when compared to measurement in still air. Same is the case with moving liquid. For measurement of accurate thermal time constant, the device needs to be placed in still air at ambient temperature. Now the thermistor is powered so that its temperature is increased. The power is maintained until the thermal equilibrium at higher temperature is reached. Now the power is cut from the thermistor and simultaneously a timer is triggered. The thermistor resistance is now continuously checked and when the body of the thermistor is cooled to 63.2%, the timer is stopped. The time showed on the timer is noted down and this time represents one time constant. The time constant is usually expressed in seconds.

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