Gas flow meter using a positive temperature coefficient thermistor as the sensor
Suman Chatterjee, Kamalendu Sengupta, Himadri Sekhar Maiti · Review of Scientific Instruments · 1999
Positive temperature coefficient (PTC) thermistor sensors have been used successfully for sensing and measurement of gas flow through a tube. Tuned detection technique using an ac signal is found to be a more efficient measuring circuit than the conventional dc Wheatstone bridge. Any particular sensor can be used to measure a wide range of flow rates using sensing heads of varying geometries. For a specific geometry, the plot of electrical voltage output against flow rate produces an “S” shaped curve which follows from the basic principles of heat transfer by both conduction and convection mechanisms.