Electrochemical force sensor

• US 5,334,304 A
• Filed: 11/18/1991
• Issued: 08/02/1994
• Est. Priority Date: 08/06/1990
• Status: Expired due to Term

• Current Assignee: Henri J.R. Maget
• Original Assignee: Henri J.R. Maget
• Inventors: Maget, Henri J. R.
• Primary Examiner(s): Tung, T.
• Application Number:
  US07/793,459
• Time in Patent Office: 988 Days
• Field of Search: 204/153.18, 204/421-429, 204/408
• US Class Current: 204/421
• CPC Class Codes: G01L 1/20 by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids of piezo-resistive materials G01L1/18; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
• CPC Class Codes: G01L 9/18 by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electric potential is produced or varied upon the application of stress

Abstract

A gas or fluid pressure or force sensor is disclosed consisting of a fluid-tight housing containing a supply of electrochemically active gas and an electrolytic membrane disposed to divide the housing into two chambers. The electrolytic membrane has one or more pervious electrodes disposed on each side of and in contact with the membrane. A flexible bellows or diaphragm is disposed to form one wall of the fluid-tight housing and provide the contacting surface for transferring a force or pressure to the sensor. A controller is connected to display measurements and to permit automatic sensor calibration, differential pressure-induced diffusion compensation, temperature compensation and sensor chamber pressure control. The disclosed force sensor is useful for application to robotic manipulators and the basic device is useful for measurement of the gas partial-pressure of a selected gas.

Claims

1. A gas pressure ratio sensor comprising:

a gas-tight housing, having two ends and a first wall at a first end;

a rigidly-supported electrolytic membrane having two sides disposed to form a second wall at a second end of said gas-tight housing and defining therein a storage chamber for holding a supply of electrochemically active gas;

at least one pervious electrode disposed on each said side of and in contact with said electrolytic membrane to form at least one opposed electrode pair;

the gas being electrochemically reversibly active so as to enter into an anodic reaction at one side of said at least one electrode pair where the gas molecules are convened to ions transportable through said electrolytic membrane and a cathodic reaction at the opposite side of said at least one electrode pair where said ions are reconverted to gas molecules; and

control means consisting essentially of at least one of the electrode pairs adapted to be responsive to a pressure differential across the electrolytic membrane, means to detect an output voltage from tile electrode pair caused by the pressure differential, which means are in electrical communication with said electrode pair, controller means in electrical communication with the detection means which are programmed to cause a current to be provided to said electrolytic membrane in response to, and sufficient to reverse, the current supplying the detected output voltage to return the pressure in the chamber to a predetermined value.

2. The gas pressure ratio sensor of claim 1 further comprising a semi-pervious covering over the portion of said electrolytic membrane disposed outside of said gas-tight housing, said semi-pervious covering being impervious to water vapor and pervious to said electrochemically active gas.

8. The sensor of claim 1, 3, or 7 wherein said electrochemically active gas is oxygen (O₂).

9. The sensor of claims 1, 3 or 7 wherein said electrochemically active gas is hydrogen (H₂).

10. The sensor of claims 1, 3 or 7 wherein additional pervious electrodes are disposed in contact with the electrolytic membrane.

11. The sensor of claims 1, 3 or 7 wherein the control means further comprise a current interrupter programmed to interrupt the current through the electrolytic membrane for at least 20 milliseconds.

12. The sensor of claim 1 or claim 7 wherein the controller means are further programmed to provide an electric bias current opposed to the direction of diffusional flow across said membrane to cancel the effects of said diffusion.

13. The sensor of claim 1 or claim 7 further comprising:

temperature sensing means for determining the temperature of said electrochemically active gas which means are in electrical communication with the controller means, wherein the controller means are further programmed to adjust for temperature variations in determining the current to be provided to the electrolytic membrane.

3. A fluid pressure sensor comprising:

a fluid-tight housing, having two ends and a first wall at a first end;

a flexible diaphragm disposed to form a second wall at a second end of said fluid-tight housing and defining therein a storage chamber for holding a supply of electrochemically active gas;

a rigidly-supported electrolytic membrane having two sides disposed between said first and second walls to divide the storage chamber into a smaller storage chamber and a sensor chamber;

at least one pervious electrode disposed on each side of and in contact with the electrolytic membrane to form at least one opposed electrode pair;

the gas being electrochemically reversibly active so as to enter into an anodic reaction at one side of said at least one electrode pair where the gas molecules are convened to ions transportable through said electrolytic membrane and a cathodic reaction at the opposite side of said at least one electrode pair where said ions are reconverted to gas molecules; and

control means consisting essentially of at least one of the electrode pairs adapted to be responsive to a pressure differential across the electrolytic membrane. means to detect an output voltage from the electrode pair caused by the pressure differential, which means are in electrical communication with said electrode pair, controller means in electrical communication with the detection means which is programmed to cause a current to be provided to said electrolytic membrane in response to, and sufficient to reverse the current supplying the detected output voltage to return the pressure in each of the chambers to a predetermined value.

4. The fluid pressure sensor of claim 3 wherein:

said fluid-tight housing is disposed inside the tip of a rigid catheter comprising a long hollow cylinder having an interior and an exterior surface.

5. The fluid pressure sensor of claim 3 wherein the controller means are further programmed to provide a electric bias current to at least one electrode pair and opposed to the direction of diffusional flow across the membrane to cancel the effects of said diffusion.

6. The fluid pressure sensor of claim 5 further comprising:

temperature sensing means for determining the temperature of said electrochemically active gas which means are in electrical communication with the controller means; and

wherein said controller means are further programmed to adjust for temperature variations in determining the current to be provided to the electrolytic membrane.

7. A force sensor/effector comprising:

a fluid-tight housing, having two ends and a first wall at a first end;

a flexible bellows having a contacting surface for transferring an external force to said sensor, said flexible bellows disposed to from a second wall at a second end of said fluid-tight housing and defining therein a storage chamber for holding a supply of electrochemically active gas;

a rigidly-supported electrolytic membrane having two sides disposed between said first and second walls to divide said storage chamber into a smaller storage chamber and a sensor chamber;

at least one pervious electrode disposed on each said side of and in contact with the etectrolylic membrane to form at least one opposed electrode pair;

said gas being electrochemically reversibly active so as to enter into an anodic reaction at one side of said at least one electrode pair where the gas molecules are convened to ions transportable through said electrolytic membrane and a carbonic reaction at the opposite side of said at least one electrode pair where said ions are reconverted to gas molecules; and

control means consisting essentially of at least one of the electrode pairs adapted to be responsive to a pressure differential across the electrolytic membrane, means to detect an output voltage from the electrode pair caused by the pressure differential, which means are in electrical communication with said electrode pair, controller means in electrical communication with the detect fort means which is programmed to cause a current to be provided to said electrolytic membrane in response to, and sufficient to reverse the current supplying the detected output voltage to return the pressure in each of the chambers to a predetermined value.