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A TDR system consists of a single coaxial cable grouted in a borehole with a TDR200 Module attached to the cable at the collar of the borehole. Readings can be taken manually with a TDR Hand-Held Readout or logged via a Datalogger. The Module sends pulsed signals along the cable which are reflected at the end of the cable and travel back to the surface where their arrival time is recorded. Reflections are also generated at places where the resistance of the cable changes, such as soil mass and rock movements or shear zones. The travel time for the reflected signal to return to the collar of the borehole is proportional to the depth at which the reflection is generated. It particularly useful in applications where shearing or deflection of the borehole requires monitoring.

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