In 1938, the first bonded, metallic wire-type strain gage was introduced. The metallic foil-type strain gage is constructed of a grid of wire filament of approximately 0.001 in thickness, bonded directly to the strained surface by a thin layer of epoxy resin.
When a load is applied to the surface, it gets strained and experiences a change in length. This resulting change in length is conveyed to the resistor and the corresponding strain is measured in terms of the electrical resistance of the foil wire, which varies linearly with strain.
Other types of Strain Gauges are described below.
- Semiconductor Strain Gauges
- Thin-film Strain Gauges
- Diffused Semiconductor Strain Gauges
- Bonded Resistance Gauges