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A compact anemometer sensitive enough to detect human breath. A refinement of the popular Wind Sensor Rev C, this design incorporates hardware ambient temperature compensation. An accurate temperature reading is made available on the interface. Based on the time-proven "hot-wire" method, this technique excels at low to medium wind speeds. Great for sensing weak indoor air movement, where the spinning cup anemometers are ineffective. 

Developed by our colleagues over at Modern Device USA, the design and application details are here.

The PCB is fully assembled and complete with loose 5pin male headers to solder on for a choice of mounting vertically (default) or horizontally.

Note that as well as the usual logic level voltage, you need an additional power feed to supply the on board regulator that provides the heating current (supply 9-12V, the load is ~40mA depending on wind speed).