Donald E Frank

US Patent:

43823351, May 10, 1983

Filed:

Jun 9, 1981

Appl. No.:

6/271752

Inventors:

Donald N. Frank - Livermore CA

Assignee:

The United States of America as represented by the United States
Department of Energy - Washington DC

International Classification:

G01B 502

US Classification:

33125B

Abstract:

A head assembly for a borehole extensometer and an improved extensometer for measuring subsurface subsidence. A plurality of inflatable anchors provide discrete measurement points. A metering rod is fixed to each of the anchors which are displaced when subsidence occurs, thereby translating the attached rod. The head assembly includes a sprocket wheel rotatably mounted on a standpipe and engaged by a chain which is connected at one end to the metering rod and at the other end to a counterweight. A second sprocket wheel connected to the standpipe also engages the chain and drives a connected potentiometer. The head assembly converts the linear displacement of the metering rod to the rotary motion of the second sprocket wheel, which is measured by the potentiometer, producing a continuous electrical output.