IMPROVEMENTS IN OR RELATING TO STRAIN GAUGES

1,203,304. Strain gauges. TAYLOR WOODROW CONSTRUCTION Ltd. March 6, 1969 [March 8, 1968], No.11556/68. Heading G1M. A strain gauge comprises an outer tube 10 e.g. of ebonite, a polyamide, a ceramic or an asbestos, an inner tube 11 of brass for example, slide fitting in the tube 10 and having gaps of #" or so between its parts 11a, 11b and 11c, platens 12 which are adapted to be embedded say in concrete, and a wire 13 which is tensioned by the platens 12 and may be plucked and vibrated by an electromagnetic device comprising a core 17 and a coil 18 which may be fed with voltage pulses via a cable 19. When the coil is energized the wire 13 vibrates and induces an E. M. F. in the coil the frequency of which corresponds to that of the wire. This frequency may be electrically measured and recorded, Fig.2 (not shown).