Thermally-matched piezoresistive elements in bridges

Patent metadata

Field	Value
Publication number	US-11099093-B2
Application number	US-201916536486-A
Country	US
Kind code	B2
Filing date	Aug 9, 2019
Priority date	Aug 9, 2019
Publication date	Aug 24, 2021
Grant date	Aug 24, 2021

Abstract

A micromechanical pressure sensor for measuring a pressure differential includes a diaphragm having an inner region and two edge regions, one opposite the other with respect to the inner region. Two or more piezoresistive resistance devices are on the diaphragm, at least one in each of the inner and edge region, and are configured to be electrically connected in a bridge circuit. The micromechanical pressure sensor is configured so that an operating temperature of the one or more piezoresistive resistance devices in the inner region is substantially the same as an operating temperature of the one or more piezoresistive resistance devices in at least one of the edge regions throughout a full operating range such that an error of the micromechanical pressure sensor output resulting from self-heating is less than if the micromechanical pressure sensor were not configured to maintain the operating temperatures substantially the same.

First claim

The invention claimed is:

1. A micromechanical pressure sensor, comprising:
a diaphragm, configured to mechanically deform in response to a load applied thereto, the diaphragm having an inner region and two edge regions, one distal the other with respect to the inner region; and
two or more piezoresistive resistance devices disposed on the diaphragm, comprising:
one or more piezoresistive resistance devices disposed in the inner region; and
one or more piezoresistive resistance devices disposed in at least one of the edge regions;

wherein:
the two or more piezoresistive resistance devices are configured to be electrically connected in a bridge circuit;
the micromechanical pressure sensor is configured so that an operating temperature of the one or more piezoresistive resistance devices disposed in the inner region is substantially the same as an operating temperature of the one or more piezoresistive resistance devices disposed in at least one of the edge regions throughout a full operating range such that an error of the micromechanical pressure sensor output resulting from self-heating is less than if the micromechanical pressure sensor were not configured to maintain the operating temperatures substantially the same;
each of the one or more piezoresistive resistance devices disposed in the inner region defines an inner resistor width;
each of the one or more piezoresistive resistance devices disposed in at least one of the edge regions defines an edge resistor width;
a ratio of the edge resistor width to the inner resistor width defines a resistor width ratio;
the resistor width ratio is less than 0 . 95 ; and
the resistor width ratio is configured so that the operating temperature of the one or more piezoresistive resistance devices disposed in the inner region is substantially the same as the operating temperature of the one or more piezoresistive resistance devices disposed in at least one of the edge regions throughout the full operating range such that the error of the micromechanical pressure sensor output resulting from self-heating is less than if the micromechanical pressure sensor were not configured to maintain the operating temperatures substantially the same.

2. The micromechanical pressure sensor of claim 1 , wherein the resistor width ratio ranges from 0.3-0.6.

3. The micromechanical pressure sensor of claim 1 , wherein:
each of the two or more piezoresistive resistance devices defines a static resistance value;
the static resistance value of each of the two or more piezoresistive resistance devices is within 10% of a particular resistance value; and
the static resistance value of each of the two or more piezoresistive resistance devices ranges from 100-50,000 ohms.

4. The micromechanical pressure sensor of claim 1 , wherein:
the bridge circuit is configured to be electrically connected to a voltage supply; and
the voltage supply ranges from 0.1-100 volts.

5. The micromechanical pressure sensor of claim 4 , wherein the voltage supply ranges from 3-50 volts.

6. The micromechanical pressure sensor of claim 1 , further comprising an isolation layer, wherein:
the isolation layer is disposed on the diaphragm; and
the two or more piezoresistive resistance devices are disposed on the isolation layer.

7. The micromechanical pressure sensor of claim 6 , wherein the isolation layer has a thickness that ranges from 0.1-5 μm.

8. The micromechanical pressure sensor of claim 1 , wherein the two or more piezoresistive resistance devices comprise:
four piezoresistive resistance devices disposed on the diaphragm, comprising:
two piezoresistive resistance devices disposed in the inner region; and
two piezoresistive resistance devices disposed in the edge regions; and

wherein the four piezoresistive resistance devices are configured to be electrically connected in a Wheatstone bridge circuit.

9. The micromechanical pressure sensor of claim 1 , further comprising one or more secondary resistance devices, wherein:
the one or more secondary resistance devices are disposed in at least one of the edge regions, one proximate each of the one or more piezoresistive resistance devices disposed in at least one of the edge regions; and
the one or more secondary resistance devices are configured to produce heat when electrical current is applied thereto, so that the operating temperature of the one or more piezoresistive resistance devices disposed in the inner region is substantially the same as the operating temperature of the one or more piezoresistive resistance devices disposed in the edge region throughout the full operating range such that the error of the micromechanical pressure sensor output resulting from self-heating is less than if the micromechanical pressure sensor were not configured to maintain the operating temperatures substantially the same.

10. The micromechanical pressure sensor of claim 9 , wherein:
each of the one or more secondary resistance devices defines a heater resistance value;
the heater resistance value ranges from 100-130,000 ohms;
each of the two or more piezoresistive resistance devices defines a static resistance value; and
a ratio of the heater resistor value to the static resistance value ranges from 1-2.6.

11. The micromechanical pressure sensor of claim 1 , further comprising two or more secondary resistance devices, wherein:
a first one or more of the two or more secondary resistance devices are disposed in at least one of the edge regions, each configured to produce heat when an electrical heating current is applied thereto, one proximate each of the one or more piezoresistive resistance devices disposed in at least one of the edge regions; and
a second one or more of the two or more secondary resistance devices are disposed in at least one of the edge regions, each configured to produce a resistance value representative of a sensed temperature, one proximate each of the one or more piezoresistive resistance devices disposed in at least one of the edge regions.

12. The micromechanical pressure sensor of claim 11 , further comprising:
one or more sensing circuits, each configured to sense the resistance value representative of a sensed temperature; and
one or more control circuits, each configured to produce the electrical heating current representative of a desired temperature.

13. The micromechanical pressure sensor of claim 11 , further comprising a first overcoat, wherein:
the first overcoat covers the first one or more secondary resistance devices disposed in the edge region; and
the second one or more secondary resistance devices is disposed on the first overcoat.

14. A method for using a micromechanical pressure sensor to measure a pressure differential across a diaphragm configured to mechanically deform in response to a load applied thereto by the pressure differential fluidly-communicated thereto, the diaphragm having an inner region and two edge regions, one edge region distal the other with respect to the inner region, the micromechanical pressure sensor comprising two or more piezoresistive resistance devices disposed on the diaphragm, the two or more piezoresistive resistance devices comprising one or more piezoresistive resistance devices disposed in the inner region each defining an inner resistor width and one or more piezoresistive resistance devices disposed in at least one of the edge regions each defining an edge resistor width, the two or more piezoresistive resistance devices configured to be electrically connected in a bridge circuit, the method comprising:
applying a supply voltage to the bridge circuit, the bridge circuit configur

Assignees

• Rosemount Aerospace Inc

Inventors

• Potasek David P
• Backman Roger Alan

Classifications

• G01L19/04 Primary

  Means for compensating for effects of changes of temperature {, i.e. other than electric compensation} · CPC title

• G01L9/0052

  of piezoresistive elements (circuits therefor G01L9/06) · CPC title

• G01L9/065 Primary

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