A cover meter is a device to determine the precise concrete cover and to pinpoint the exact location of the rebars in the concrete. The cover depth of the concrete has a major impact on those processes that lead to the corrosion of the rebars. Hitting a rebar while boring into reinforced concrete can destroy the drilling instrument or even weaken the concrete structure.
Trying to avoid rebars, however, can be a tedious and difficult process. Therefore it is vital know the cover depth and the precise location of the rebars before starting the maintenance work. Since the eddy-current principle with pulse-induction is the most economical solution, most cover meters are based on this principle.
In the case of double layer arrangements of the rebars it is suggested to start the location with the first layer. If the layers are too close to each other, it is likely to be impossible to locate the bars of the second layer.
For precise determination of the bar diameter it is important to verify that there are no unnoticed influences that could falsify the result. Therefore it is recommended to select a place on the structure where there is sufficient spacing between the rebars. It must also kept in mind that the cover depth of the concrete influences the accuracy of the cover meters. The accuracy of the cover meters decreases with the depth of the concrete cover.
The standards BS 1881:204 (Testing concrete. Recommendations on the use of electromagnetic covermeters) and the DIN 1045 (Guideline Concrete, reinforcement and prestressed concrete structures) can be applied to the cover meter.