Patent ID: 6568276
Filing Date: 2003-05-27
Classification: G01L

Abstract:
A strain gauge based pressure sensor, comprising:a diaphragm frame in the general shape of a tube, said tube defining an outer surface generally centered on an axis and having a transverse cross-sectional first geometric shape defining a transverse outer dimension, and also defining a central bore, also generally centered on said axis, said central bore defining a cross-sectional second geometric shape, which may be the same as said first geometric shape, said bore defining a maximum transverse dimension smaller than said transverse outer dimension of said first geometric shape; an active diaphragm monolithic with said diaphragm frame, said active diaphragm generally defining a diaphragm plane transverse to said axis, said active diaphragm closing off a distal end of said diaphragm frame, whereby the closed-off distal end of said diaphragm frame can withstand fluid pressure, but said active diaphragm deflects in an outward direction, away from said bore, in response to pressure within said bore, said active diaphragm having a generally uniform thickness dimension measured in a direction parallel with said axis between inner and outer surfaces of said diaphragm, the ratio of the square of said generally uniform thickness dimension of said diaphragm divided by said transverse dimension of said bore having a value greater than about 0.029; a plurality of strain gauges mounted on an outer surface of said active diaphragm for generating a pressure-related signal in response to said deflection of said active diaphragm; said diaphragm frame further defining at least one annular groove extending from said outer surface of said diaphragm frame radially inward toward said axis, to a depth insufficient to open said annular groove into said bore, said annular groove defining two planar, mutually parallel, annular walls, the planes of which annular walls are distal from said diaphragm plane and generally parallel therewith, said at least one groove thereby acting to effectively â€œseparateâ€  a distal-most portion of said diaphragm frame from that portion of said diaphragm frame more proximal than said annular groove, which in turn tends to reduce â€œsphericalâ€  deflection of said active diaphragm.