Thermal flow micro sensors

A review is given on sensors fabricated by silicon micromachining technology using the thermal domain for the measurement of fluid flow. Attention is paid especially to performance and geometry of the sensors. Three basic types of thermal flow sensors are discussed: anemometers, calorimetric flow sensors and time of flight flow sensors. Anemometers may comprise several heaters and temperature sensors and from a geometric point of view are similar sometimes for calorimetric flow sensors. We find that depending on the Reynolds number to or three element anemometers may perform as calorimetric sensors (very small Re) while calorimetric flow sensors operate like anemometers in the high Re regime