Fine linearity control in integral silicon transducers

Claim 2

An integral silicon pressure transducer comprising: a circular, restrained edge silicon diaphragm that develops bending stresses in response to applied pressure and has a preselected radius, said diaphragm having an inherent mechanical nonlinearity with applied pressure, a plurality of strain gages formed integrally on said diaphragm including at least one central gage subject to tensile strain and one outer gage subject to compressive strain, and circuit means for connecting said strain gages in a resistance bridge circuit that generates an output voltage as a measure of the applied pressure, said outer gage being located at a radial position on said diaphragm to produce a predetermined nonlinear bridge resistance variation with applied pressure to compensate for the inherent mechanical nonlinearity of said diaphragm, so as to thereby generate a substantially linear output voltage.

Claim 3

A pressure transducer according to claim 1 in which the difference between the strains experienced by said central and outer gages determines the nonlinear bridge resistance variation and has a selected positive value.

Claim 4

A pressure transducer according to claim 2 further including a mounting member with an internal bore to which the edges of said silicon diaphragm are secured.

Claim 5

A pressure transducer according to claim 2 in which said central and outer gages have a fixed pattern and radial separation, and the diaphragm radius is variable according to the pressure range being measured.

Claim 6

An integral silicon pressure transducer comprising: a circular single crystal n-type silicon diaphragm that develops bending stresses and has an inherent mechanical nonlinearity with applied pressure, and a mounting member restraining the edges of said diaphragm at a preselected radius, a fixed p-type silicon pattern formed integrally on one surface of said diaphragm including a pair of central strain gages that are symmetrical with the center of said diaphragm and subject to tensile strain and a pair of diametrically spaced outer strain gages subject to compressive strain, said p-type pattern further including low resistance areas connecting said strain gages as a resistance bridge circuit, contact pads for connection of a source of energy, and other contact pads for detecting the output voltage of said bridge circuit, said preselected radius locating said outer gages at radial positions on said diaphragm to produce a predetermined nonlinear bridge resistance variation with applied pressure to compensate for the inherent mechanical nonlinearity of said diaphragm, so as to thereby generate a substantially linear output voltage.

Claim 7

An integral silicon pressure transducer comprising: a circular single crystal n-type silicon diaphragm that develops bending stresses and has an inherent mechanical nonlinearity with applied pressure, and a mounting member restraining the edges of said diaphragm at a preselected radius, a fixed p-type silicon pattern formed integrally on one surface of said diaphragm including a pair of central strain gages that are symmetrical with the center of said diaphragm and subject to tensile strain and a pair of diametrically spaced outer strain gages subject to compressive strain, said p-type pattern further including low resistance areas connecting said strain gages as a resistance bridge circuit, contact pads for connection of a source of energy, and other contact pads for detecting the output voltage of said bridge circuit, said preselected radius locating said outer gages at radial positions on said diaphragm to produce a predetermined nonlinear bridge resistance variation with applied pressure to compensate for the inherent mechanical nonlinearity of said diaphragm, so as to thereby generate a substantially linear output voltage.

Claim 8

A pressure transducer according to claim 5 in which the difference between the strain experienced by one of said central gages and the strain experienced by one of said outer gages determines the bridge resistance variation and has a positive value.

Claim 9

A pressure transducer according to claim 6 in which said mounting member is a tube with an inside diameter corresponding to double the preselected diaphragm radius.

Claim 10

A pressure transducer according to claim 7 in which the inside diameter of the mounting tube and diaphragm radius are variable according to the pressure range being measured.