A cover meter (sometimes called a pachometer) is a nondestructive testing device for locating steel in concrete and masonry structures. The principle of the meter is that the field of an electromagnet is affected by the presence of steel.
The meter is based on a pulse-induction eddy current design and consists of two parts, a locating probe and the meter itself that has a display giving the dimension of the cover over the steel or a signal strength reading. The locating probe of the cover meter is a rectangular encapsulated unit containing a directional search coil. An audible indication is also provided by the meter that gives a guide to signal strength and location of embedded steel.