Description

DEMEC* strain gauge manufactured by WH Mayes & Son of Stroud, UK. Fitted wooden box.

It is a high-precision mechanical instrument used to measure strain or cracking across a structure. By taking manual readings between pre-established gauge points, it allows engineers and researchers to track structural deformation, cracking, and stress over time.

The gauge is mounted on a steel bar with two hardened steel tips (conical points) set 8 in (203.2 mm) apart: one end of the bar is fixed while the other end is allowed to pivot and any movement of the pivot can be read on a dial and any strain calculated. It is used in conjunction with matching setting-out and reference bars also held in the collection (see here).

Where there is suspected strain or cracking, two pre-drilled stainless steel discs are secured to the surface of a test area and a setting-out bar is used to set an exact initial distance. Subsequently, to determine if there has been any movement the gauge’s two tips are placed into the pre-drilled locating discs on the reference bar to set the gauge to the initial set distance. The gauge can then be applied to the two discs set up on the test area and any difference in length can be read from the dial.

This gauge was used in the Concrete Laboratory at Heriot-Watt University, Edinburgh, UK.

*DEMEC = demountable mechanical