Resistive strain gauge pressure sensor

• US 5,174,158 A
• Filed: 06/07/1991
• Issued: 12/29/1992
• Est. Priority Date: 06/07/1991
• Status: Expired due to Fees

• Current Assignee: MacLean-Fogg Company
• Original Assignee: MacLean-Fogg Company
• Inventors: Kremidas, James R.
• Primary Examiner(s): WOODIEL, DONALD
• Application Number:
  US07/711,947
• Time in Patent Office: 571 Days
• Field of Search: 73/708, 73/706, 73/720, 73/721, 73/726, 73/727, 73/753, 73/754, 73/DIG. 4, 73/756, 338/4, 338/42
• US Class Current: 73/721
• CPC Class Codes: G01L 19/003 using a detachable interface or adapter between the process medium and the pressure gauge
• CPC Class Codes: G01L 19/0038 being part of the housing other details about the housing G01L19/14
• CPC Class Codes: G01L 19/0084 to the outside of the housing other details about the housing see G01L19/14
• CPC Class Codes: G01L 19/142 Multiple part housings
• CPC Class Codes: G01L 19/143 Two part housings
• CPC Class Codes: G01L 9/0051 using variations in ohmic resistance
• CPC Class Codes: G01L 9/0055 bonded on a diaphragm

Abstract

A resistive strain gauge pressure sensor including upper and lower housings coacting to define a pressure chamber within the housing. A board member is clamped between the housings and defines a diaphragm portion which extends across the pressure chamber to divide the pressure chamber into upper and lower chamber portions. All of the circuitry of the sensor is screen printed onto the lower planar face of the board member including the various resistor elements of the strain gauge assembly, the various elements of the conditioning circuit receiving the output of the strain gauge assembly, and the various further leads required to connect the circuitry elements to the terminals of the sensor. The sensor terminals are provided by a plurality of connector pins extending downwardly through the board member for connection at their respective lower ends to the circuitry provided on the lower face of the board member.

Claims

1. A resistive strain gauge pressure sensor including a diaphragm exposed to a pressure to be sensed, a resistive strain gauge assembly positioned on the diaphragm and operative to generate an output signal in response to flexing of the diaphragm, and a conditioning circuit receiving the output signal from the strain gauge assembly and operative to generate a sensor output signal, characterized in that the sensor includes a board member having a relatively thin portion defining a diaphragm portion and a relatively thick portion defining a substrate portion, the board defines a generally flat planar surface including one side surface of the diaphragm portion and one side surface of the substrate portion, the strain gauge assembly is positioned on said one side surface of said diaphragm portion, the conditioning circuit is positioned on said one side surface of said substrate portion, and the sensor further includes a plurality of connector pins extending through said substrate portion and terminating proximate said flat planar surface to define terminals for connection to said conditioning circuit and said strain gauge assembly.

2. A transducer comprising:

a housing defining a chamber;

a board member defining a relatively thick substrate portion and a relatively thin diaphragm portion and including a flat planar surface extending across said substrate portion and said diaphragm portion;

means mounting said board member in said housing with said diaphragm portion extending across said chamber to divide said chamber into an upper chamber portion above said diaphragm portion and a lower chamber portion below said diaphragm portion and sealed from said upper chamber;

a resistive strain gauge assembly positioned on said planar surface proximate said diaphragm portion operative to receive a voltage input and generate a voltage output in response to flexing of the diaphragm portion;

terminal means on said planar surface proximate said substrate portion;

means electrically connecting said terminal means to said strain gauge assembly so as to allow the transmittal of a voltage input of said strain gauge assembly; and

conditioning circuit means on said planar surface proximate said substrate portion receiving the voltage output of said strain gauge assembly and operative to condition said voltage output and transmit the conditioned voltage output to said terminal means to enable the transmittal of a conditioned voltage output signal from said terminal means.

3. A transducer according to claim 2 wherein said strain gauge assembly and said conditioning circuit are printed onto said planar surface.

4. A transducer according to claim 2 wherein said housing defines a further chamber and said substrate portion of said board assembly extends across said further chamber.

5. A resistive strain gauge pressure sensor comprising:

an upper housing;

a lower housing coacting with said upper housing to define a pressure chamber;

a board member clamped at its periphery between said upper and lower housings and including a relatively thick substrate portion and a relatively thin diaphragm portion extending across said pressure chamber to divide said pressure chamber into an upper pressure chamber above said diaphragm portion and a lower pressure chamber below said diaphragm portion and sealed from said upper chamber, said board member defining a generally flat planar surface extending across one side surface of said diaphragm portion and one side surface of said substrate portion;

a resistive strain gauge assembly positioned on said flat planar surface on said one side surface of said diaphragm portion and having an input and an output;

terminal means on said flat planar surface on said one side surface of said substrate portion; and

means connecting said terminal means to the input of said strain gauge assembly, whereby to provide a voltage input signal to said strain gauge assembly, and connecting the output of said strain gauge assembly to said terminal means, whereby to provide a sensor output signal at the terminal means.

6. A sensor according to claim 5 wherein said sensor includes a conditioning circuit positioned on said substrate portion and electrically interconnected between the output of said strain gauge assembly and said terminal means so as to condition the output signal from said strain gauge assembly prior to transmittal to said terminal means.

7. A sensor according to claim 6 wherein said board member defines a generally planar surface and said strain gauge assembly and said conditioning circuit are positioned on said planar surface in side-by-side relation.

8. A differential pressure sensor including a housing defining a pressure chamber, a diaphragm extending across the chamber to divide the chamber into an upper chamber portion in communication with a first fluid pressure and a lower chamber portion in communication with a second fluid pressure, and a resistive strain gauge assembly positioned on the diaphragm and operative in response to flexing of the diaphragm to generate an output signal proportional to the pressure differential between the upper and lower chamber portions, characterized in that the housing further defines an instrumentation chamber laterally displaced from and sealed from the pressure chamber, the sensor includes a board member extending laterally within the housing and including a relatively thin diaphragm portion constituting the diaphragm of the sensor and a relatively thick substrate portion extending across the instrumentation chamber, the strain gauge assembly is positioned on the diaphragm portion with the pressure chamber, and the sensor further includes a conditioning circuit positioned on the substrate portion within the instrumentation chamber and electrically connected to the output of the strain gauge assembly.

9. A sensor according to claim 8, wherein the sensor further includes terminal means positioned on the substrate portion within the instrumentation chamber and electrically connected respectively to the input of the strain gauge assembly and the output of the conditioning circuit.

10. A sensor according to claim 9, wherein the strain gauge assembly, the conditioning circuit, and the terminal means are provided on the lower surface of the board member and the terminal means are provided by connector pins extending downwardly through the board member to define the terminal means at their lower ends.