Patent ID: 7878056

Claim:
A micromachined thermal mass flow sensor with self-cleaning components comprising: a suspending membrane with an resonant cavity underneath; a heater thermistor being disposed on top of said suspending membrane; an upstream temperature sensing thermistor being disposed on top of said suspending membrane; a downstream temperature sensing thermistor being disposed on top of said suspending membrane; a reference thermistor being disposed on top of a region of non-suspending membrane; a top electrode being formed by in serial connecting said heater thermistor, said upstream temperature sensing thermistor, and said downstream temperature sensing thermistor by an external circuit; and a bottom electrode being formed by a doped polysilicon layer or a metal layer which is disposed on a bottom surface of said resonant cavity; wherein the self-cleaning components of said thermal mass flow sensor generate a mechanical vibration on said suspending membrane by modulating an electric voltage between said top and bottom electrodes of said resonant cavity such that foreign particles are detached and blown away by a gas flow from the top surface of said suspending membrane.