Integral silicon diaphragms for low pressure measurements

Claim 2

An integral silicon transducer for measuring a predetermined range of low pressures comprising a restrained-edge silicon diaphragm that has preselected geometry and a high area-to-thickness ratio so as to develop both bending stresses and significant membrane stresses in response to low applied pressures less than 5 psi, a plurality of silicon strain gages formed integrally on said diaphragm including a pair of active gages located at approximate coordinate positions at which the strain is substantially linear as the pressure changes within the predetermined range of low pressures, and circuit means for connecting said pair of active gages in a resistance measuring circuit having a substantially linear output voltage.

Claim 3

An integral silicon transducer for measuring a predetermined range of low pressures comprising a circular, restrained-edge silicon diaphragm that has a preselected radius and a high radius-to-thickness ratio greater than 10 so as to develop both bending stresses and significant membrane stresses in response to low applied pressures less than 5 psi, a plurality of silicon strain gages formed integrally on said diaphragm including a first pair of active gages located at the approximate diametrically spaced radial positions at which the strain is substantially linear as the pressure changes within the predetermined range of low pressures, and circuit means for connecting said first pair of gages in a resistance measuring circuit having a substantially linear output voltage.

Claim 4

An integral silicon transducer for measuring a predetermined range of low pressures comprising a circular, restrained-edge silicon diaphragm that has a preselected radius and a high radius-to-thickness ratio greater than 10 so as to develop both bending stresses and significant membrane stresses in response to low applied pressures less than 5 psi, a plurality of silicon strain gages formed integrally on said diaphragm including a first pair of active gages located at the approximate diametrically spaced radial positions at which the strain is substantially linear as the pressure changes within the predetermined range of low pressures, and circuit means for connecting said first pair of gages in a resistance measuring circuit having a substantially linear output voltage.

Claim 5

An integral silicon transducer for measuring a predetermined range of low pressures comprising a circular, restrained-edge silicon diaphragm that has a preselected radius and a high radius-to-thickness ratio so as to develop both bending and membrane stresses in response to low applied pressures, a plurality of silicon strain gages formed integrally on said diaphragm including at least a first pair of active gages located at the approximate radial position at which the strain is substantially linear as the pressure changes within the predetermined range of low pressures, and circuit means for connecting said first pair of gages in a resistance measuring circuit having a substantially linear output voltage, in which said radial position is approximately r/a 0.54, where r iS the radial distance from the center of the diaphragm to the center of the active gage, and a is the preselected diaphragm radius.

Claim 6

An integral silicon transducer for measuring a predetermined range of low pressures comprising a circular, restrained-edge silicon diaphragm that has a preselected radius and a high radius-to-thickness ratio so as to develop both bending and membrane stresses in response to low applied pressures, a plurality of silicon strain gages formed integrally on said diaphragm including at least a first pair of active gages located at the approximate radial position at which the strain is substantially linear as the pressure changes within the predetermined range of low pressures, and circuit means for connecting said first pair of gages in a resistance measuring circuit having a substantially linear output voltage, in which said radial position is approximately r/a 0.54, where r iS the radial distance from the center of the diaphragm to the center of the active gage, and a is the preselected diaphragm radius.

Claim 7

A pressure transducer according to claim 3 in which said first pair of active gages are on one side of said diaphragm aligned in the same crystallographic direction and are subjected to tensile strains.

Claim 8

A pressure transducer according to claim 4 further including a second pair of passive gages on the same side of said diaphragm aligned in a relatively non-strain sensitive crystallographic direction, said circuit means connecting said first and second pair of gages in a half-active full bridge circuit.

Claim 9

A pressure transducer according to claim 4 further including a second pair of active gages formed integrally on the other side of said diaphragm aligned in the same crystallographic direction and subjected to compressive strains, said circuit means connecting said first and second pair of gages in a fully active full bridge circuit.

Claim 10

An integral silicon transducer for measuring a predetermined range of low pressures comprising a circular, restrained-edge, n-type single crystal silicon diaphragm that has a preselected radius and a high radius-to-thickness ratio so as to develop both bending and membrane stresses in response to low applied pressures, a p-type silicon pattern formed integrally on said diaphragm including at least a first pair of diametrically spaced active strain gages subjected to tensile strain located at the approximate radial position r/a 0.54 at which the strain is substantially linear as the pressure changes within the predetermined range of low pressures, where r is the radial distance from the center of the active diaphragm to the center of the active gage, and a is the preselected diaphragm radius, said p-type silicon pattern further including a second pair of strain gages and connection means for connecting said first and second pair of strain gages as a full resistance bridge circuit.

Claim 11

An integral silicon transducer for measuring a predetermined range of low pressures comprising a circular, restrained-edge, n-type single crystal silicon diaphragm that has a preselected radius and a high radius-to-thickness ratio so as to develop both bending and membrane stresses in response to low applied pressures, a p-type silicon pattern formed integrally on said diaphragm including at least a first pair of diametrically spaced active strain gages subjected to tensile strain located at the approximate radial position r/a 0.54 at which the strain is substantially linear as the pressure changes within the predetermined range of low pressures, where r is the radial distance from the center of the active diaphragm to the center of the active gage, and a is the preselected diaphragm radius, said p-type silicon pattern further including a second pair of strain gages and connection means for connecting said first and second pair of strain gages as a full resistance bridge circuit.

Claim 12

A pressure transducer according to claim 7 in which said second pair of strain gages are diametrically spaced relatively non-strain sensitive strain gages located on the same side of said diaphragm as said first pair of active strain gages, and said connection means are provided by low resistance areas and contact pads interconnecting said first and second pairs of strain gages.

Claim 13

A pressure transducer according to claim 8 in which said first pair of active strain gages are oriented in the <110> crystallographic direction and said second pair of non-strain sensitive strain gages are oriented in the <100> crystallographic direction on a (110) plane n-type silicon diaphragm.

Claim 14

A pressure transducer according to claim 7 in which said second pair of strain gages are diametrically spaced active strain gages located on the other side of said diaphragm at the radial position r/a 0.54 so as to be subjected to compressive strains, and said connection means are provided by through-connections interconnecting said first and second pairs of strain gages.

Claim 15

A pressure transducer according to claim 8 in which said first and second pair of strain gages are both oriented in the <110> crystallographic direction on a (110) plane n-type silicon diaphragm.