Sensor element assembly and method
Described herein is the sense element assembly for a capacitive pressure sensor and method for creating same that has increased sensitivity without additional size. The sense element assembly and method includes fabricating an off-centered elliptically shaped center electrode, at least one elliptical annular-like electrode around the center electrode, a ground electrode and a method for fusing the layers together to optimize sensitivity.
1. A sensor element for a capacitive sensor comprising:
a substrate assembly comprising:
a substrate having a center,
a first elliptically shaped electrode on the substrate having a first conductive terminal;
a second substantially annular elliptically shaped electrode surrounding and not touching the first electrode, and the second electrode having a second conductive terminal;
a diaphragm assembly comprising:
a diaphragm,
a ground electrode on the diaphragm having a ground conductive terminal;
wherein the substrate assembly is sealed to the diaphragm assembly.
2. The sensor element assembly of claim 1 , wherein the first and the second electrodes are offset from the center of the substrate.
3. The sensor element assembly of claim 2 wherein the major diameters of the first and second electrodes are as large as possible while still retaining sufficient space between the perimeter of the second electrode and the perimeter of the substrate, wherein a good seal between the substrate assembly and the diaphragm assembly around the periphery thereof is created.
4. The sensor element assembly of claim 1 further comprising a shield extending from the second terminal around said first terminal.
5. The sensor element assembly of claim 1 , wherein the first and second elliptical electrodes are shaped such that the major diameter of the second electrode will provide essentially the same outside seal width as the minor diameter of the second electrode.
6. The sensor element assembly of claim 1 further comprising at least one or more frits that cause a substantially symmetrical seal when the substrate and diaphragm assemblies are sealed together.
7. A method for fabricating a pressure sense element assembly for a capacitive pressure sensor, the method comprising the steps of:
printing a first substantially elliptical electrode and a second substantially elliptical annular electrode onto a substrate,
firing the electrodes,
printing a first frit over the electrodes and substrate,
drying the first frit;
assembling a diaphragm by printing the common/ground electrode,
firing the common/ground electrode,
printing a second frit over the common/ground electrode and the diaphragm,
drying the second frit; and
firing the first or second frit; and
fusing the diaphragm onto which the ground electrode has been fabricated to the substrate onto which the first and second elliptical electrodes have been fabricated to create the sensor assembly.
8. The method of claim 7 wherein the step of printing the electrodes onto the substrate comprises offsetting the first and second electrodes on the substrate.
9. The method of claim 7 further comprising creating a gap in the frit areas wherein the frit areas create a substantially symmetrical seal.
10. A sensor element for a capacitive sensor comprising:
a substrate having a center, a first electrode off-center on the substrate having a first conductive terminal area;
a second substantially annular electrode surrounding and not touching the first electrode, and the second electrode having a second conductive terminal area;
a diaphragm,
a ground electrode on the diaphragm having a ground conductive terminal; and
one or more seals for sealing the substrate to the diaphragm.
11. The sensor element assembly of claim 10 wherein the major diameters of the first and second electrodes are as large as possible while still retaining sufficient space between the perimeter of the second electrode and the perimeter of the substrate to create a good seal when the substrate and the diaphragm are sealed together.
12. The sensor element assembly of claim 10 wherein the first and second electrodes are elliptically shaped.
13. The sensor element assembly of claim 10 , wherein the first and second electrodes are shaped such that the major diameter of the second electrode will provide essentially the same outside seal width as the minor diameter of the second electrode.