Used for measuring strain in steel members, the strain gauge can be welded to load bearing beams, tunnel segments, struts, sheet pile walling and tendons. The gauge is adjustable to suit compression or tension.

The gauge consists of a sealed tube containing the vibrating wire, which is factory welded to two pads, one at either end, which in turn are spot welded on site to the structural members to be monitored.  With the gauge spot welded to the structure, deformation of the steel mass (member) causes the two welded points to move relative to one another, thus altering the tension in the steel wire and its natural frequency. As the gauge is attached directly to the structure then an externally housed electromagnetic excitation coil, sealed within a PVC housing situated at the mid-point of the gauge tube, is used to excite the strained wire. Connected by tough 4-core, screened cable, the coil is activated by an electrical pulse from a vibrating wire readout unit, which then measures the resulting frequency of vibration. Using a gauge factor, the measured frequency may be converted directly into units of strain.