The Model 3900 Embedment Strain Gage is designed for the measurement of dynamic strains in concrete structures, earth fills and soils. Special high-temperature versions are also available for use in asphalt. It comprises a full bridge strain gaged proving ring coupled, between two flanges, with a spring and shaft. When the flanges move relative to one another, the tension in the spring changes and hence the strain in the proving ring. A PVC tube serves as a protective housing and holds the gage at the desired initial tension.