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NTC Thermistors are excellent devices to detect changes in thermal dissipation of a sensed media. Using their self-heating characteristics, the NTC Thermistor can be heated to a point above ambient conditions. The power required to reach this temperature is proportional to the dissipation of the media being sensed. - A simplified convection equation explains the heat transfer mechanism: dq=h⋅dA(Tfluid−Tsensor). The value of “h” is related to the Reynolds number of the fluid, which varies with velocity. The temperature differential between the fluid and the sensor impacts heat transfer, which is related to the sensor's ability to dissipate the heat generated in the NTC.
- Using the NTC in pulsed mode allows the circuit to determine the initial fluid temperature at time = zero. By controlling the power and measuring either the current or voltage drop at the end of the power cycle, one can determine the rate of flow through a fixed orifice, such as a pipe or passageway.
- In applications requiring metered flow, detection of flow obstructions can trigger an alarm, alerting the system or operator to maintenance needs.
