Patent ID: 6684695
Filing Date: 2004-02-03
Classification: G01F

Abstract:
A sensor for measuring the mass flow of a fluid stream moving through a chamber comprising:a thermal insulating substrate projecting into the chamber and extending in the direction of the fluid stream whereby said fluid stream flows past said substrate, said substrate having a leading and a trailing edge; spaced first and second resistors on the substrate, said first resistor being located upstream in the fluid stream from the second resistor; spaced third and fourth spaced resistors on the substrate, said third resistor being located upstream in the fluid stream from the fourth resistor; said first, second, third and fourth resistors being located on said substrate a sufficient distance inwardly from the leading and trailing edges and having a height H approximately one-half or greater than the height of the fluid stream to be within the velocity recovery region of the fluid stream and to be subjected to nearly the entire velocity profile of the fluid stream as the stream moves across the resistors and past the substrate; means for changing the temperature of the fluid stream as it passes between the first and second resistors and between the third and fourth resistors; a Wheatstone bridge circuit having first, second, third and fourth legs, each of said legs containing a respective one of the first, second, third and fourth resistors; and an external circuit connected to the Wheatstone bridge circuit for receiving a signal from the Wheatstone bridge circuit and for developing an output signal indication of the fluid stream flowing through the chamber.