Thermal mass flow meter and method of making same

Abstract

A thermal mass flow meter includes a comb-shaped structure having a plurality closely spaced septa carried from a common spine and disposed within the flow stream to be measured for partitioning the flow therein into a plurality of generally parallel elongated ribbon-shaped flow stream portions. Temperature-dependent fluid flow sensing resistor means is coupled in heat-exchanging relation predominantly with the narrow face of at least one of said ribbon-shaped flow stream portions for measuring the fluid flow. In a preferred embodiment, the comb-shaped flow partitioning structure is fabricated by anisotropically etching the parallel flow channels through the (110) face of diamond cubic material such as silicon. In another embodiment, a thermal loading member is disposed in heat-exchanging relation with the temperature dependent fluid flow sensing resistor means for thermally loading same and pushing the critical flow rate up to a higher flow to allow operation of the flow sensor in one mode of operation over a wider range of flow rates.

Dependencies are inferred from the claim text.