Pressure sensor with improved strain gauge

Patent metadata

Field	Value
Publication number	US-10557770-B2
Application number	US-201715704797-A
Country	US
Kind code	B2
Filing date	Sep 14, 2017
Priority date	Sep 14, 2017
Publication date	Feb 11, 2020
Grant date	Feb 11, 2020

Abstract

An apparatus senses a pressure of a fluid from a fluid medium. The apparatus has a port body with a peripheral wall surrounding an interior channel. The interior channel extends between a diaphragm on the port body and an opening for receiving the fluid. A strain gauge is disposed on the port body. The strain gauge has two or more resistors connected between input/output pads and ground pads. The resistors are spaced substantially equidistant from the ground pad to reduce mobile ion migration.

First claim

What is claimed is:

1. An apparatus for sensing a pressure of a fluid from a fluid medium comprising:
a port body having a peripheral wall surrounding an interior channel for receiving the fluid from the fluid medium, the interior channel extending between the fluid medium and a diaphragm on the port body;
a strain gauge affixed to the port body by a glass substrate, the strain gauge comprising: a first resistor electrically connected between a first input/output (I/O) pad and a ground pad; a second resistor electrically connected between a second I/O pad and the ground pad; a third resistor electrically connected between a third I/O pad and the ground pad; and a fourth resistor electrically connected between a fourth I/O pad and the ground pad;
four current sources, each current source providing a uniform, constant current to one of the I/O pads;
a first output electrically connected between the first I/O pad and the second I/O pad for measuring voltage; and
a second output electrically connected between the third I/O pad and the fourth I/O pad for measuring voltage,
wherein:
each resistor is spaced substantially equidistant from the ground pad to urge uniform mobile ion accumulation across the resistors; and
when the diaphragm experiences pressure from the fluid: the second resistor and the third resistor experience a tension force; and the first resistor and fourth resistor experience a compression force.

2. An apparatus for sensing a pressure of a fluid from a fluid medium comprising:
a port body having a peripheral wall surrounding an interior channel, the interior channel extending between a diaphragm on the port body and an opening for receiving the fluid; and
a strain gauge disposed on the port body comprising: a first resistor electrically connected between a first input/output (I/O) pad and a ground pad; a second resistor electrically connected between a second I/O pad and the ground pad; a third resistor electrically connected between a third I/O pad and the ground pad; and a fourth resistor electrically connected between a fourth I/O pad and the ground pad,
wherein each resistor is substantially equidistant from the ground pad to reduce mobile ion migration.

3. The apparatus of claim 2 wherein a uniform input is applied through each resistor simultaneously.

4. The apparatus of claim 2 wherein:
the first I/O pad and the second I/O pad are disposed on a first side of the ground pad; and
the third I/O pad and the fourth I/O pad are disposed on a second side of the ground pad.

5. The apparatus of claim 4 wherein the I/O pads and the ground pad are arranged in a parallel row.

6. The apparatus of claim 2 wherein the resistors are piezoresistive elements.

7. The apparatus of claim 2 wherein:
the first resistor and the fourth resistor are positioned adjacent to the peripheral wall and the second resistor and the third resistor are positioned adjacent to the diaphragm, such that fluid in the interior channel causes the first and fourth resistors to experience compression while the second and third resistors experience tension.

8. The apparatus of claim 2 wherein the first resistor and the fourth resistor are symmetrical to the second resistor and the third resistor about a lateral axis passing through the I/O pads.

9. The apparatus of claim 2 wherein:
the ground pad is elongated along a longitudinal axis; and
the first resistor and the second resistor are symmetrical about the longitudinal axis to the fourth resistor and the third resistor.

10. An apparatus for sensing a pressure of a fluid from a fluid medium comprising:
a strain gauge comprising: a first resistor electrically connected between a first input/output (I/O) pad and a ground pad; a second resistor electrically connected between a second I/O pad and the ground pad; a first output electrically connected between the first I/O pad and the second I/O pad; a third resistor forming a first resistor pair with the second resistor; and a fourth resistor forming a second resistor pair with the first resistor, wherein,
wherein:
the first and second resistors are spaced from the ground pad to urge uniform mobile ion accumulation across the first and second resistors: and
the first resistor pair and the second resistor pair are symmetrical about a lateral axis.

11. The apparatus of claim 10 wherein the resistors are spaced substantially equidistant from the ground pad.

12. The apparatus of claim 10 wherein a constant current is applied through the first resistor and the second resistor, the constant current being uniform.

13. The apparatus of claim 12 wherein:
the constant current is applied to the first resistor via the first I/O pad;
the constant current is applied to the second resistor via the second I/O pad; and
the output measures a change in voltage between the first I/O pad and the second I/O pad.

14. The apparatus of claim 13 wherein the first I/O pad, the second I/O pad, and the ground pad are aligned along a lateral axis, the first resistor and the second resistor being symmetrical about the lateral axis.

15. The apparatus of claim 10 wherein a constant voltage is applied through the first resistor and the second resistor, the constant voltage being uniform.

16. The apparatus of claim 10 wherein the strain gauge further comprises:
the third resistor electrically connected between a third I/O pad and the ground pad;
the fourth resistor electrically connected between a fourth I/O pad and the ground pad; and
a second output electrically connected between the third I/O pad and the fourth I/O pad.

17. The apparatus of claim 16 further comprising a port body defining an interior channel for receiving the fluid from the fluid medium, wherein the strain gauge is disposed on the port body.

18. The apparatus of claim 17 wherein the port body is conductive and grounded.

19. The apparatus of claim 17 wherein:
the first resistor and the fourth resistor are positioned adjacent to a peripheral wall of the port body surrounding the interior channel such that fluid in the channel causes the first resistor and the fourth resistor to experience a compression force; and
the second resistor and the third resistor are positioned adjacent to a diaphragm within the port body, the diaphragm being exposed to the interior channel, such that fluid in the channel causes the second resistor and the third resistor to experience a tension force.

20. The apparatus of claim 16 wherein:
the first resistor and the second resistor form a first resistor pair;
the third resistor and the fourth resistor form a second resistor pair; and
the first resistor pair and the second resistor pair are symmetrical about a longitudinal axis.

Assignees

• Sensata Technologies Inc

Inventors

• Huo Shihong
• Wolf Eric A
• Petrarca Neil S

Classifications

• G01L19/00

  Details of, or accessories for, apparatus for measuring steady or quasi-steady pressure of a fluent medium insofar as such details or accessories are not special to particular types of pressure gauges · CPC title

• G01L9/0002

  using variations in ohmic resistance (G01L9/0051 takes precedence) · CPC title

• G01L9/06

  of piezo-resistive devices · CPC title

• G01L1/22

  using resistance strain gauges · CPC title

• G01L1/2287

  constructional details of the strain gauges (adjustable resistors H01C10/00) · CPC title