High sensitivity pressure sensor with long term stability
First Claim
1. A high sensitivity pressure sensor with long term stability comprising:
- a housing including first and second chambers;
a membrane separating the first and second chambers;
a first electrode located in the first chamber and spaced from one side of the membrane forming a first capacitor therewith;
a second electrode located in the second chamber and spaced from an opposite side of the membrane forming a second capacitor therewith;
a measuring circuit connected across the first and second capacitors for measuring membrane displacement by detecting differences in capacitance between the first and second capacitors; and
a compensation circuit configured to apply an electric field to the membrane as a compensating force and to reduce the voltage difference between the first electrode and the membrane and to increase the voltage difference between the second electrode and the membrane to provide long term stability.
1 Assignment
0 Petitions
Accused Products
Abstract
A high sensitivity pressure sensor with long term stability including a housing with first and second chambers, a membrane separating the first and second chambers, a first electrode located in the first chamber and spaced from one side of the membrane forming a first capacitor therewith, and a second electrode located in the second chamber and spaced from an opposite side of the membrane forming a second capacitor therewith. A measuring circuit is connected across the first and second capacitors for measuring membrane displacement by detecting differences in capacitance between the first and second capacitors and a compensation circuit is configured to apply an electric field to the membrane as a compensating force by reducing the voltage difference between the first electrode and the membrane and simultaneously increasing the voltage difference between the second electrode and the membrane or vice versa to provide long term stability. The invention also features a unique compensation circuit for a pressure sensor and a method of making and operating a pressure sensor.
-
Citations
72 Claims
-
1. A high sensitivity pressure sensor with long term stability comprising:
-
a housing including first and second chambers;
a membrane separating the first and second chambers;
a first electrode located in the first chamber and spaced from one side of the membrane forming a first capacitor therewith;
a second electrode located in the second chamber and spaced from an opposite side of the membrane forming a second capacitor therewith;
a measuring circuit connected across the first and second capacitors for measuring membrane displacement by detecting differences in capacitance between the first and second capacitors; and
a compensation circuit configured to apply an electric field to the membrane as a compensating force and to reduce the voltage difference between the first electrode and the membrane and to increase the voltage difference between the second electrode and the membrane to provide long term stability. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71)
-
-
26. A high sensitivity pressure sensor with long term stability comprising:
-
a housing including first and second chambers;
a metal membrane separating the first and second chambers, the metal membrane not under significant tension in the absence of a differential pressure between the two chambers;
a first electrode located in the first chamber and spaced from one side of the metal membrane forming a first capacitor;
a second electrode located in the second chamber and spaced from an opposite side of the metal membrane forming a second capacitor;
a measuring circuit for measuring membrane displacement by detecting differences in capacitance between the first and second capacitors; and
a compensation circuit including a voltage divider connected to the first and second electrodes and having a middle point which when unbalanced applies a greater electric field to one side of the membrane than the other side of the membrane.
-
-
27. A high sensitivity pressure sensor with long term stability comprising:
-
a housing including first and second chambers;
a metal membrane separating the first and second chambers;
a first electrode located in the first chamber and spaced from one side of the metal membrane forming a first capacitor;
a second electrode located in the second chamber and spaced from an opposite side of the metal membrane forming a second capacitor;
the housing made of a material having a coefficient of thermal expansion the same as or substantially the same as the coefficient of thermal expansion of the material of the membrane;
a measuring circuit connected across the first and second capacitors for measuring membrane displacement by detecting differences in capacitance between the first and second capacitors; and
a compensation circuit configured to apply an electric field to the membrane as a compensating force and to reduce the voltage difference between the first electrode and the membrane and to increase the voltage difference between the second electrode and the membrane.
-
-
28. A high sensitivity pressure sensor with long term stability comprising:
-
a housing including first and second chambers;
a metal membrane separating the first and second chambers;
a first electrode located in the first chamber and spaced from one side of the metal membrane forming a first capacitor; and
a second electrode located in the second chamber and spaced from an opposite side of the metal membrane forming a second capacitor, the metal membrane not under significant tension in the absence of a differential pressure between the two chambers.
-
-
45. A high sensitivity pressure sensor with long term stability comprising:
-
a housing including first and second chambers;
a metal membrane separating the first and second chambers;
a first electrode located in the first chamber and spaced from one side of the metal membrane forming a first capacitor; and
a second electrode located in the second chamber and spaced from an opposite side of the metal membrane forming a second capacitor, the housing made of a material having a coefficient of thermal expansion the same as or substantially the same as the coefficient of thermal expansion of the material of the membrane.
-
-
46. A control circuit for a differential pressure sensor including first and second capacitors and a membrane common to both capacitors, the control circuit comprising:
-
a measuring circuit connected across the first and second capacitors for measuring membrane displacement by detecting differences in capacitance between the first and second capacitors; and
a compensation circuit configured to initially apply an equal voltage and electric field to both sides of the membrane, and apply a compensating force by reducing the voltage difference between the first electrode and the membrane simultaneously increasing the voltage difference between the second electrode and the membrane or vice versa to provide long term stability.
-
-
47. A high method of making and using a high sensitivity pressure sensor with long term stability, the method comprising:
-
forming a housing to include first and second chambers;
disposing a membrane to separate the first and second chambers;
placing a first electrode in the first chamber spaced from one side of the membrane forming a first capacitor therewith;
placing a second electrode in the second chamber spaced from an opposite side of the membrane forming a second capacitor therewith;
connecting a measuring circuit across the first and second capacitors for measuring membrane displacement by detecting differences in capacitance between the first and second capacitors; and
initially applying an equal strength electric field to each side of the membrane, and applying a compensating force by reducing the voltage difference between the first electrode and the membrane and simultaneously increasing the voltage difference between the second electrode and the membrane or vice versa to provide long term stability.
-
-
72. A method of operating a high sensitivity pressure sensor to have long term stability wherein the pressure sensor includes a housing with first and second chambers, a metal membrane separating the first and second chambers, a first electrode located in the first chamber and spaced from one side of the membrane forming a first capacitor, a second electrode located in the second chamber and spaced from an opposite side of the metal membrane forming a second capacitor, the method comprising:
-
measuring membrane displacement by detecting differences in capacitance between the first and second capacitors; and
initially applying an electric field of equal magnitude to each side of the membrane, and applying a compensating force by reducing the voltage difference between the first electrode and the membrane and simultaneously increasing the voltage difference between the second electrode and the membrane or vice versa.
-
Specification