Measuring instrument for determining displacements in soil, rock, foundation soil or construction materials

A measuring instrument for determining displacements in a material, which comprises:

• first and second hinge-coupled elongate, substantially rigid measuring elements for being positioned in the material;
• and
• a measuring device for determining changes of position of the first and second measuring elements relative to each other, brought about by pivoting of the first measuring element relative to the second measuring element, wherein the measuring device includes a flexible element interconnecting the first and second measuring elements and a mechanism for determining the curvature or bending of the flexible element, which occurs by pivoting of the first measuring element relative to the second measuring element, as a measure of relative displacement in the material by the first and second measuring elements relative to each other, wherein the mechanism for determining the curvature or bending of the flexible element comprises a wire strain gage, fitted on at least one side of the flexible element, and a converter for converting elongations of the flexible element into at least one of proportional electric current and voltage signals and wherein the flexible element includes a wire strain gage on each of four outer surfaces thereof, each said surface succeeding a preceding surface at a central angle of 90.degree., said the wire strain gages including circuitry for determining displacements in the material in mutually perpendicular directions.