US 5,528,939 A · Micromechanical pressure gauge having extended sensor range

Abstract

An improved gas pressure gauge is disclosed that extends the linear range of pressure dependent damping to higher pressures by placing a stationary member in very close proximity to the vibrating member. This range of linear dependent damping is also extended to lower pressures by making the vibrating member large in area relative to its small distance from a fixed planar member, which can also serve as its supporting member, by making it vibrate in a direction perpendicular to the fixed planar member, and by making the springs that support the vibrating member from a high Q and conductive material, such as boron doped single crystal silicon. These features for extending the range to higher and lower pressures can be built separately into two independent vibrating elements that can be used individually or in tandem, or they can be built into a single vibrating element that can be made to vibrate in two modes, one parallel and one perpendicular to a fixed member. The preferred method of measuring gas pressure with these gauges is to determine the drive voltage necessary to drive the mechanical oscillator to a fixed amplitude against the pressure dependent damping of the gas that is being measured.

Claims34

Dependent claims

A micromechanical pressure gauge comprising:

a stationary member, said stationary member having a planar surface with a first conductive path and a first conductive electrode electrically coupled thereto;
at least one vibrating member to act as a second conductive electrode and having a second conductive path, said vibrating member operably attached to said stationary member in proximity thereof and electrically coupled thereto, wherein a distance between said stationary and vibrating members is comparable to a mean free path of a molecule of a gas between said stationary and vibrating member;
an electrical oscillator connected to said first and second conductive paths for inducing mechanical vibrations of a predetermined oscillation amplitude in said vibrating member, whereby said vibrating member operates in an extended molecular drag regime;
and
means for measuring a drive voltage required to maintain said predetermined oscillation amplitude in the presence of a pressure dependent damping of said vibrating member, said drive voltage being proportional to a total pressure of said gas.

2 more elements

A micromechanical pressure gauge comprising:

a stationary member, said stationary member made of an electrically insulative material and having at least one substrate electrode, each said electrode having a respective substrate conductive path coincident therewith and operably coupled thereto;
a plurality of vibrating members secured on said stationary member in proximity thereof, said vibrating members each having a mass, means for supporting said mass, a mass electrode coincident with the mass and operably coupled thereto, and a mass conductive path operably coupled to said mass electrode and electrically connecting said vibrating members to said stationary member wherein a distance between said stationary member and each vibrating member is comparable to a mean free path of a molecule of a gas residing between said stationary and each vibrating member;
an electrical oscillator connected to said conductive paths for inducing and maintaining mechanical vibrations of a predetermined oscillation amplitude in each said vibrating members in the presence of a pressure dependent damping, whereby said vibrating members each operate over a specified portion of an extended molecular drag regime;
and
means for measuring a drive voltage necessary for maintaining said predetermined mass oscillation amplitude, said drive voltage being proportional to a total pressure value of said gas.

2 more elements

Dependencies are inferred from the claim text.

Micromechanical pressure gauge having extended sensor range

Life of this patent

Micromechanical pressure gauge having extended sensor range

Life of this patent

Abstract

Claims34