Stress gauge

• US 4,860,587 A
• Filed: 05/31/1988
• Issued: 08/29/1989
• Est. Priority Date: 05/31/1988
• Status: Expired due to Fees

• Current Assignee: Carl E. Keller
• Original Assignee: Carl E. Keller
• Inventors: Keller, Carl E.
• Primary Examiner(s): Noland, Tom
• Application Number:
  US07/200,419
• Time in Patent Office: 455 Days
• Field of Search: 73/784, 73/774, 73/763, 73/773
• US Class Current: 73/774
• CPC Class Codes: G01L 25/00 Testing or calibrating of apparatus for measuring force, torque, work, mechanical power, or mechanical efficiency

Abstract

This invention is a stress gauge whose components include a piezoresistive sensor embedded in epoxy, a flatjack, and a housing for the sensor and flatjack. The preferred piezoresistive sensor is ytterbium because of its sensitivity to pressures in the range of interest. This arrangement allows the gauge sensing element to be calibrated at the place of measurement. That calibration is provided by a well controlled uniaxial load applied to the gauge to test the gauge response. Upon removal of the applied load, the gauge can continue to measure the stress history of the surrounding medium.

Claims

1. An electrical stress gauge comprising:

a. a stress sensor material which generates a voltage proportional to applied stress;

b. electrical insulating means surrounding said sensor;

c. a closed housing surrounding said sensor and insulating means;

d. a flat jack positioned with said housing and overlying said sensor in closely spaced parallel relation, thereto,

e. conduit means extending through said housing and affording connection of a source of pressurized fluid to said flat jack for uniaxial loading of said sensor; and

f. conductive means extending through said housing affording electrical connection to said sensor.

2. A stress gauge as defined by claim 1 in which said housing permits only a uniaxial load on said sensor.