A micro-range thermal gas mass flow sensor is researched and fabricated. The sensor chip is fabricated by micro-electro-mechanical system（ MEMS） process

includes two upstream

and two downstream temperature measurement resistors and environmental resistors. The four upstream and downstreammeasuring resistors are symmetrically distributed in the center of chip

which constitute a Wheatstone bridge. During operation

the chip is driven by constant voltage mode. When the gas flows over the surface of the chip

the bridge is unbalanced and changes of flow signal is transformed to voltage signal. Output curre of sensor is calibrated through experiments and the precision of the sensor is tested. Test result shows that at the flow range of 0

5 m L/min the sensor has the advanta

ges of fast response

high precision

and so on.