Abstract: A MEMS flow sensor is provided having a micro flow channel etched in a silicon structure composed of two silicon substrates bonded or fused together. A heater and one or more temperature sensors are, in one embodiment, disposed around the perimeter of the flow channel and outside of the channel. In another embodiment, a heater and one or more temperature sensors are respectively disposed outside the flow channel at the top and bottom of the channel. In further embodiments, a heater and one or more temperature sensors are located inside the flow channel on one or more surfaces thereof or around the inside perimeter of the channel. The flow sensors in accordance with the invention are preferably fabricated using wafer scale fabrication techniques.

Abstract: The present invention provides a MEMS thermal flow sensor or meter for measuring the flow rate of a fluid without need for calibration of the flow sensor for that particular fluid. A response curve is determined by plotting the sensor output voltage against the volume flow rate divided by fluid thermal diffusivity for a calibration fluid of known thermal diffusivity, and storing response curve data in memory. A conversion factor is employed to provide a measure of correct flow rate of an unknown fluid. This conversion factor is derived from the ratio of the thermal time constant of the calibration fluid to the thermal time constant of the measured fluid, the time constants being measured at zero flow. These time constants are stored in memory. This conversion factor in conjunction with the response curve data is utilized by the processor to produce the correct flow rate.