Patent ID: 8650946

Claim:
A thermal flow sensor for measuring flow of a fluid, the sensor comprising: a cyclic flow modulator comprising: a common flow channel portion and a bifurcated flow channel portion; an electromechanical actuator; a perforate rotor turnable about an axis by the electromechanical actuator; and a perforate stator co-axial with the rotor, wherein the perforations in the rotor and stator cooperate to provide a minimum flow impedance between the common flow channel portion and one of the two bifurcated flow channel portions when providing a maximum flow impedance between the common flow channel portion and the other of the bifurcated flow channel portions, each minimum flow impedance state characterized by a plurality of respective perforations in the rotor being aligned with a corresponding plurality of respective perforations in the stator; two electrically heated temperature sensitive elements respectively disposed to receive fluid flowing through respective bifurcated channel portions, whereby the two temperature sensitive elements generate respective cyclic signals indicative of respective amounts of heat removed therefrom by the flowing fluid; and thermal flow signal processing circuitry operable to receive the cyclic signals and to determine therefrom the rate of flow.