The instrument is based on the pulse-induction technique. A repetitive current pulse is applied to the coils in the search head whose magnetic field induces eddy currents in a bar located below the search head. The instrument measures the amplitude of the induced current, which depends on the orientation, depth and size of the bar.
To identify the location and orientation of the rebar under the surface of the concrete, a search head is connected to the covermeter and is used to scan across the designated search area. When the bar is positioned below the center of the search head, the signal strength will be at its maximum by which the instrument measures the depth of the position and estimates the diameter size. The technique is uniquely stable, is not affected by moisture in concrete or magnetic aggregates and is immune to temperature variations and electrical interference.
A range of fully interchangeable search heads are available to suit different requirements. Changing from one search head to another is quick and simple.
The CoverMaster (Elcometer 331) can also be used with half-cell electrode probes to measure half-cell potentials in accordance with ASTM C876, in a similar manner to the Mini Grate Dane (see its technical data sheet).