THERMAL EFFECT AND OFF-CENTER LOAD COMPENSATION OF A SENSOR

• US 20090167327A1
• Filed: 12/28/2007
• Published: 07/02/2009
• Est. Priority Date: 12/28/2007
• Status: Active Grant

• Current Assignee: Ypoint Capital, Inc,
• Original Assignee: Ypoint Capital, Inc,
• Inventors: HARISH, DIVYASIMHA
• Granted Patent: US 8,191,428 B2
• Time in Patent Office: Days
• US Class Current: 324/685
• CPC Class Codes: G01L 1/142 using capacitors
• CPC Class Codes: G01L 19/04 Means for compensating for effects of changes of temperature , i.e. other than electric compensation
• CPC Class Codes: G01L 9/0075 using a ceramic diaphragm, e.g. alumina, fused quartz, glass
• CPC Class Codes: Y10T 29/53174 Means to fasten electrical component to wiring board, base, or substrate

Abstract

A method and system of thermal effect and off-center load compensation of a sensor are disclosed. In one embodiment, a sensor includes a first conductive surface and a second conductive surface substantially parallel to the first conductive surface, a processing and communication zone of the first conductive surface and the second conductive surface having circuitry to enable communication with an external system (e.g., using a Universal Serial Bus (USB) interface) and a sensing area having partially a ceramic substrate surrounding a sensor surface and a reference surface of the first conductive surface and the second conductive surface. The sensor may include a set of electrical leads that enable the sensing area to communicate with the processing and communication zone and with external devices, and a guard ring surrounding the first conductive surface and the second conductive surface to minimize an effect of stray capacitance.

Claims

1. A sensor, comprising:

a first conductive surface and a second conductive surface substantially parallel to the first conductive surface;

a processing and communication zone of at least one of the first conductive surface and the second conductive surface having circuitry to enable communication with an external system; and

a sensing area having at least partially a ceramic substrate surrounding at least one of a sensor surface and a reference surface of at least one of the first conductive surface and the second conductive surface.

2. The sensor of claim 1 wherein the circuitry to enable communication with the external system is through a Universal Serial Bus (USB) interface.

3. The sensor of claim 1 wherein the circuitry is a wireless enabled circuitry that enables the sensor to operate through a wireless network including at least one of a Bluetooth network, a WiFi network, and a ZigBee network.

4. The sensor of claim 1 wherein a portion of at least one of the processing and communication zone and the sensing area is fabricated with a FR4 printed circuit board material adjacent to the ceramic substrate to reduce cost of manufacture of the sensor.

5. The sensor of claim 1 further comprising a set of electrical leads that enable the sensing area to communicate with the processing and communication zone and with external devices, and a guard ring surrounding at least one of the first conductive surface and the second conductive surface to minimize an effect of stray capacitance.

6. The sensor of claim 1 wherein the ceramic substrate comprises essentially of alumina created through a form of aluminum oxide, Al2O3, occurring naturally as corundum, in a hydrated form in bauxite, and with various impurities among which include ruby, sapphire, and emery.

7. The sensor of claim 6 wherein the ceramic substrate has a low thermal expansion coefficient that is well matched to a housing of the sensor, and wherein the housing of the sensor is a stainless steel material.

8. The sensor of claim 7 further comprising a film material to bond the ceramic substrate to the housing of the sensor after a roughness pattern is introduced on the housing to better secure the bond between the ceramic substrate and the housing of the sensor, wherein the roughness takes on a spiral grove pattern, and wherein the film provides a more linear thermal characteristic thereby making error correction of the sensor simpler.

9. The sensor of claim 8 wherein a jig having a preset force is applied to the ceramic substrate and the housing to minimize hysteresis of the sensor, and wherein the film compresses from 3 mils to 1 mil when 350 degrees F. temperature is applied for 10 minutes using a thermoset process.

10. The sensor of claim 7 wherein the ceramic substrate is attached to the housing three stainless steel spacers of 10 mils a piece.

11. The sensor of claim 7 wherein a glass layer is created between the housing and the ceramic substrate such that ceramic substrate rests above the glass layer separating it from the housing.

12. The sensor of claim 7 wherein the ceramic substrate is directly fused to the housing a 900 degree F. temperature process optimized to minimize air bubbles between the ceramic substrate and the housing.

13. The sensor of claim 1 wherein multiple sensing zones make up the sensor surface to minimize tilt in case of off-center loading.

14. The sensor of claim 13, further comprising a curved surface of at least one of the sensor surface, first conductive surface, and the second conductive surface to keep an area between a set of plates predictable when off-center loading occurs.

15. The sensor of claim 14, further comprising a double-diaphragm sensor with a hollow interior cavity housing surrounding a solid central portion to minimize tilt effects due to off-center loading, wherein the double-diaphragm sensor has physical properties of a three dimensional four bar linkage swept across an axis.

16. A method, comprising:

surrounding a sensing area of a sensor with a ceramic material that has a thermal coefficient of expansion which is well matched to a housing of the sensor;

applying a film to secure the sensing area and the ceramic material to a housing of the sensor; and

reducing a tilt that affects a measurement of the sensor by creating at least one of a double-diaphragm pattern of the housing and curving at least one plate of the sensing area such that an area between the at least one plate and another plate does not substantially change when an off-center load is applied on the sensor.

17. The method of claim 16 further comprising fabricating a portion of at least one of the processing and communication zone and the sensing area with a FR4 printed circuit board material adjacent to a ceramic substrate to reduce cost of manufacture of the sensor;

and

creating a roughness pattern on the housing to better secure a bond between the ceramic substrate and the housing of the sensor, wherein the roughness takes on a spiral grove pattern, and wherein the film provides a more linear thermal characteristic thereby making error correction of the sensor simpler.

18. The method of claim 16 in a form of a machine-readable medium embodying a set of instructions that, when executed by a machine, cause the machine to perform the method of claim 16.

19. A sensor, comprising:

a ceramic substrate surrounding at least one of a sensor surface and a reference surface of the sensor;

a film material to bond the ceramic substrate to a housing of the sensor after a roughness pattern is introduced on the housing to better secure the ceramic substrate and the housing of the sensor; and

a hollow interior cavity of the sensor in a double-diaphragm form surrounding a solid central portion to minimize tilt effects due to off-center loading, wherein the double-diaphragm form has physical properties of a three dimensional four bar linkage swept across an axis.

20. The sensor of claim 19, further comprising:

a curved surface of the sensor surface to keep an area between a set of plates predictable when off-center loading occurs.