The Geosense® VW Deformation Meter is a long-base strain gauge, designed to measure deformations in rock, concrete or soil. It can also be embedded in soils in embankments such as earth dams and road fills. Base lengths of the gauge can vary from a minimum off 0.3 metres to more than 25 metres.
When used in rock, in horizontal or inclined downward boreholes, grouting is the most common method of installation. In overhead boreholes, a special grouting apparatus of hydraulic anchors are required.
For direct placement into concrete the deformation meter can be easily tied to the rebar cage.
Each extensometer contains a VW displacement transducer which converts extensions between the flanges into an electrical signal. The frequency is transmitted through cables to the readout or data logger. These values, when multiplied by a calibration constant give the displacement of the flanges.