ABSTRACT
Flow sensors are used to measure the speed of a plane versus the surrounding air. This is an important parameter for flight stability since the speed generates the uplift force of the wings. A number of macroscopic devices measure the flow by mechanic principles, such as small turbines, drag force moving up a probe body against gravity or filling of a defined volume (inverted pump). There are several macroscopic flow measurement systems, which are powerful but cannot be realized as micro sensors. Most thermal anemometers use constant power, because it is simpler to implement, but constant temperature is also applied. For differential pressure flow sensing, it was the other way round: flat characteristics at flow low rate and low dynamic range, plus the danger of membrane braking at overload.
