Development of long-length wire filament strain gages

An extra long wire filament strain gage to ensure the integrity of an epoxy/sand/gravel plug for an underground explosion was developed. Extra long gages were required because it was important to know the strain level of the entire plug and commercial gages were typically less than 6 in. long. The extra long gages were designed and fabricated with lengths of between 1 and 10 ft; they weighed between 2 and 25 lb. The gages were fabricated by wrapping a fine filament wire onto a structural skeleton which was potted into a mold using the same epoxy/sand/gravel mixture as the plug. This results in a gage package that can be emplaced before the bulk of the plug is poured. Gages are built with both temperature compensating dummy legs and active Poisson legs included in the package.