Dual balanced capacitance manometers for suppressing vibration effects

A capacitive pressure sensor comprising:

• a common source of an unknown pressure;
• a first capacitance manometer that receives said unknown pressure to produce a first signal indicative of said unknown pressure, said first capacitance manometer positioned in a first location where a vibrational or gravitational force applied to said sensor causes a positive change in said first signal;
• and
• a second capacitance manometer that receives said unknown pressure to produce a second signal indicative of said unknown pressure, said second capacitance manometer positioned in a second location where a vibrational or gravitational force applied to said sensor causes a negative change in said second signal,
• said first and second signals combined to provide a pressure measurement responsive to a difference between said first and second signals, said pressure measurement sensitive to changes in said unknown pressure of at least as low as 1 micro-torr.

A capacitive pressure sensor comprising:

• means for providing an unknown pressure to a common pressure chamber;
• first capacitive measurement device that receives said unknown pressure and that produces a first signal indicative of said unknown pressure, said first measurement device positioned so that application of a vibrational or gravitational force to said pressure sensor produces a first change in said first signal;
• second capacitive measurement device uncoupled from said first capacitive measurement device and that operates independently to receive said unknown pressure and to produce a second signal indicative of said unknown pressure, said second measurement device positioned so that application of said vibrational or gravitational force to said pressure sensor produces a second change in said second signal, and
• a circuit that receives and combines said first and second signals from said first and second capacitive measurement devices to generate a sensor output signal responsive to said unknown pressure, said circuit combining said first and second signals such that changes in said first and second signals caused by vibrational or gravitational forces cancel, said sensor output signal having a sensitivity to said unknown pressure to changes at least as small as 1 micro-torr.

A method of measuring an unknown pressure in the presence of vibrational or gravitational forces, comprising the steps of:

• providing said unknown pressure to first and second capacitance manometers, each of said capacitance manometers having a sensitivity sufficient to be affected by a vibrational or gravitational force such that measurements of very low pressures are distorted by said vibrational or gravitational force;
• producing a first signal indicative of said unknown pressure from said first capacitance manometer;
• producing a second signal indicative of said unknown pressure from said second capacitance manometer;
• positioning said first and second capacitance manometers with respect to each other so that said vibrational or gravitational force produces a first change in said first signal produced by said first capacitance manometer and said vibrational or gravitational force produces a second change in said second signal produced by said second capacitance manometer, said capacitance manometers selected so that said first change and said second change are substantially similar in magnitude and opposite in sign;
• and
• combining said first and second signals to provide a third signal, wherein said third signal is unaffected by either said first or second changes in the signals respectively produced by said first and second capacitance manometers such that said third signal provides an accurate indication of said unknown pressure with a sensitivity as low as at least 1 micro-torr.

A pressure sensor comprising:

• a common pressure chamber receiving a varying pressure;
• a first flexible member positioned adjacent said common pressure chamber such that at least a portion of said first flexible member moves in response to variations in said variable pressure and said portion further moves in a first direction in response to a vibrational or gravitational force;
• a first fixed member positioned relative to said first flexible member such that said first fixed member and said first flexible member form a first sensor which produces a first signal responsive to said movement of said first flexible member, and where movement of said first flexible member in said first direction produces a positive change in said first signal;
• a second flexible member positioned adjacent said common pressure chamber such that at least a portion of said second flexible member moves in response to variations in said variable pressure and said portion further moves in said first direction in response to said vibrational or gravitational force;
• a second fixed member positioned relative to said second flexible member such that said second fixed member and said second flexible member form a second sensor which produces a second signal responsive to said movement in said second flexible member and where movement of said second flexible member in said first direction produces a negative change in said second signal;
• and
• a component adjustable after the manufacture of said pressure sensor which applies an adjustable linearly-variable weight to and adds together each of said first and second signals, so that said first and second signals, when weighted by said component after adjustment, sum to a value approximately equal to zero in response to movement of said flexible members induced by vibrational and gravitational forces.

A pressure sensor comprising:

• a common source of an unknown pressure;
• a thermostatically-controlled oven, said oven maintaining said pressure sensor at a constant temperature, thereby minimizing changes in the operation of said pressure sensor caused by thermal expansion or contraction of the materials comprising said pressure sensor and thereby minimizing condensation within said pressure sensor;
• a first capacitance manometer that receives said unknown pressure to produce a first signal indicative of said unknown pressure, said first capacitance manometer positioned in a first location where a vibrational or gravitational force applied to said sensor causes a positive change in said first signal;
• and
• a second capacitance manometer that receives said unknown pressure to produce a second signal indicative of said unknown pressure, said second capacitance manometer positioned in a second location where a vibrational or gravitational force applied to said sensor causes a negative change in said second signal.

A pressure sensor comprising:

• a common pressure chamber;
• an inlet that communicates an unknown pressure to said common pressure chamber;
• a first measuring device that receives said unknown pressure and that produces a first signal indicative of said unknown pressure, said first measuring device positioned so that application of a vibrational or gravitational force to said pressure sensor produces a first change in said first signal;
• a second measuring device that receives said unknown pressure and that produces a second signal indicative of said unknown pressure, said second measuring device positioned so that application of said vibrational or gravitational force to said pressure sensor produces a second change in said second signal;
• an electrical circuit capable of adjustment after the manufacture of said pressure sensor which applies a linearly-variable weight factor to each of said first and second signals and sums the weighted first and second signals, said weight factor chosen to cancel the dependence of the pressure reading of said pressure sensor on vibrational motion and gravitational forces;
• and
• a thermostatically-controlled oven, said oven maintaining said pressure sensor at a constant temperature to minimize the effects of thermal expansion and contraction on said pressure sensor and to minimize the effects on said pressure sensor of condensation.