Patent ID: 7107834

Claim:
A mass flow rate sensor, having a predetermined bypass ratio, for measuring a mass flow rate of a gas, comprising: a main conduit for containing a gas flow; a sensor passageway configured to tap a portion of the gas flow from the main conduit at a first location and to return the portion of the gas flow to the conduit at a second location, wherein the sensor passageway has an entrance length (Le s ) as a function of the gas and flow rate, and a total length (L s ), wherein the sensor passageway is configured to produce an entrance effect (Leff s ) in the portion of gas flowing therein that is approximately equal to Le s /L s ; and a plurality of bypass passageways positioned in the main conduit between the first location and the second location, wherein each of the bypass passageways has an entrance length (Le b ) as a function of the gas and flow rate, and a total length (L b ), wherein each bypass passageway is configured to produce an entrance effect (Leff b ) in gas flowing therewithin (Le b /L b ) that is substantially equal to the entrance effect of the sensor passageway (Le s /L s ) so that the bypass ratio remains substantially the same for any type of gas flowing through the sensor.