Pressure sensor with trim resistors

Patent metadata

Field	Value
Publication number	US-11768121-B2
Application number	US-202117532687-A
Country	US
Kind code	B2
Filing date	Nov 22, 2021
Priority date	Nov 22, 2021
Publication date	Sep 26, 2023
Grant date	Sep 26, 2023

Abstract

A pressure sensor includes a Wheatstone bridge circuit including a first resistor, a second resistor, a third resistor, and a fourth resistor having matching output characteristics. The pressure sensor further includes a first trim resistor in series with the Wheatstone bridge circuit, wherein the first trim resistor has output characteristics matching the output characteristics of the first resistor, the second resistor, the third resistor, and the fourth resistor of the Wheatstone bridge. The pressure sensor additionally includes a second trim resistor in parallel or a parallel loop with the Wheatstone bridge circuit, wherein the second trim resistor has output characteristics matching the output characteristics of the first resistor, the second resistor, the third resistor, and the fourth resistor of the Wheatstone bridge.

First claim

The invention claimed is:

1. A pressure sensor comprising:
a Wheatstone bridge circuit including a first resistor, a second resistor, a third resistor, and a fourth resistor having matching output characteristics;
a first trim resistor in series with the Wheatstone bridge circuit, wherein the first trim resistor has output characteristics matching the output characteristics of the first resistor, the second resistor, the third resistor, and the fourth resistor of the Wheatstone bridge circuit; and
a second trim resistor in parallel or a parallel loop with the Wheatstone bridge circuit, wherein the second trim resistor has output characteristics matching the output characteristics of the first resistor, the second resistor, the third resistor, and the fourth resistor of the Wheatstone bridge circuit; and
a third trim resistor in series with the Wheatstone bridge circuit, wherein the third trim resistor has output characteristics that are mismatched to the output characteristics of the first resistor, the second resistor, the third resistor, and the fourth resistor of the Wheatstone bridge circuit.

2. The pressure sensor of claim 1 , wherein two of the first resistor, the second resistor, the third resistor, and the fourth resistor are oriented to increase in resistance due to an applied pressure, and two of the first resistor, the second resistor, the third resistor, and the fourth resistor are oriented to decrease in resistance due to the applied pressure.

3. The pressure sensor of claim 1 , wherein the first trim resistor and the second trim resistor have a temperature coefficient of resistance that is the same as a temperature coefficient of resistance of the first resistor, the second resistor, the third resistor, and the fourth resistor.

4. The pressure sensor of claim 1 , wherein the first trim resistor and the second trim resistor are made out of the same material and/or have the same thickness as the first resistor, the second resistor, the third resistor, and the fourth resistor of the Wheatstone bridge circuit.

5. The pressure sensor of claim 1 , wherein the first trim resistor can be trimmed to change a span of the Wheatstone bridge circuit, and wherein the second trim resistor can be trimmed to change a nominal voltage output of the Wheatstone bridge circuit.

6. The pressure sensor of claim 1 , and further comprising:
a fourth trim resistor in parallel with the Wheatstone bridge circuit, wherein the fourth trim resistor has output characteristics that are mismatched to the output characteristics of the first resistor, the second resistor, the third resistor, and the fourth resistor of the Wheatstone bridge circuit.

7. The pressure sensor of claim 6 , wherein the third trim resistor and the fourth trim resistor have a temperature coefficient of resistance that is different than a temperature coefficient of resistance of the first resistor, the second resistor, the third resistor, and the fourth resistor.

8. The pressure sensor of claim 6 , wherein the first resistor, the second resistor, the third resistor, and the fourth resistor of the Wheatstone bridge circuit are positioned on a pressure die, and wherein the first trim resistor, the second trim resistor, the third trim resistor, and the fourth trim resistor are positioned on a trim die separate from the pressure die.

9. A pressure sensor comprising:
a Wheatstone bridge circuit including a first resistor, a second resistor, a third resistor, and a fourth resistor having matching output characteristics;
a first trim resistor electrically coupled to the Wheatstone bridge circuit, wherein the first trim resistor has output characteristics matching the output characteristics of the first resistor, the second resistor, the third resistor, and the fourth resistor of the Wheatstone bridge circuit; and
a second trim resistor electrically coupled to the Wheatstone bridge circuit, wherein the second trim resistor has output characteristics that are mismatched to the output characteristics of the first resistor, the second resistor, the third resistor, and the fourth resistor of the Wheatstone bridge circuit.

10. The pressure sensor of claim 9 , wherein the first trim resistor has a temperature coefficient of resistance that is the same as a temperature coefficient of resistance as the first resistor, the second resistor, the third resistor, and the fourth resistor, and wherein the second trim resistor has a temperature coefficient of resistance that is different than the temperature coefficient of resistance as the first resistor, the second resistor, the third resistor, and the fourth resistor.

11. The pressure sensor of claim 9 , wherein the first trim resistor is made out of the same material and/or has the same thickness as the first resistor, the second resistor, the third resistor, and the fourth resistor of the Wheatstone bridge circuit.

12. The pressure sensor of claim 9 , wherein the first trim resistor can be trimmed to change a span or a nominal voltage output of the Wheatstone bridge circuit, and wherein the second trim resistor can be trimmed to temperature compensate a span or a nominal voltage output of the Wheatstone bridge circuit.

13. The pressure sensor of claim 9 , wherein the first resistor, the second resistor, the third resistor, and the fourth resistor of the Wheatstone bridge circuit are positioned on a pressure die, and wherein the first trim resistor and the second trim resistor are positioned on a trim die separate from the pressure die.

14. A pressure sensor comprising:
a first sensor portion having a pressure die with piezoresistors located in a Wheatstone bridge circuit configuration; and
a second sensor portion having a trim die with a first trim resistor positioned on the trim die;
wherein the pressure die in the first sensor portion is electrically coupled to the trim die in the second sensor portion; and
wherein the first sensor portion and the second portion are positioned apart from one another.

15. The pressure sensor of claim 14 , wherein the first sensor portion further comprises:
a housing; and
a cavity extending from a first end to a second end of the housing;
wherein the pressure die is positioned in a first cavity portion of the cavity and surrounded by a pressure transfer fluid to hermetically seal the pressure die in the first sensor portion.

16. The pressure sensor of claim 14 ,
wherein the pressure die further comprises:
a diaphragm wafer having an outer portion and a diaphragm;
a first insulating layer on first surfaces of the outer portion and the diaphragm, wherein the piezoresistors of the Wheatstone bridge circuit are positioned on a first surface of the first insulating layer over the diaphragm;
a second insulating layer on a first surface of the first insulating layer and first surfaces of the piezoresistors of the Wheatstone bridge circuit; and
a protection layer on a first surface of the second insulating layer; wherein the trim die further comprises:
a trim wafer having a wafer portion;
a first insulating layer on a first surface of the wafer portion, wherein the first trim resistor is positioned on a first surface of the first insulating layer;
a second insulating layer on a first surface of the first insulating layer and a first surface of the first trim resistor; and
a protection layer on a first surface of the second insulating layer;

wherein the outer portion and the diaphragm of the diaphragm wafer are made out of the same material as the wafer portion of the trim wafer;
wherein the first insulating layer of the diaphragm wafer is made out of the same mater

Assignees

• Rosemount Aerospace Inc

Inventors

• Potasek David P
• Stuelke Robert

Classifications

• G01L9/065 Primary

  with temperature compensating means (non electric temperature compensating means G01L19/04) · CPC title

• G01R27/08

  Measuring resistance by measuring both voltage and current · CPC title

• G01L19/02

  Arrangements for preventing, or for compensating for, effects of inclination or acceleration of the measuring device; Zero-setting means (for aneroid barometers G01L7/14) · CPC title

• G01L9/045

  with electric temperature compensating means (non electric temperature compensating means G01L19/04) · CPC title

• G01L9/025

  with temperature compensating means (non electric temperature compensating means G01L19/04) · CPC title