Earthing Measuring Instruments

An earthing measuring instrument, also known as an earth megger, is a test device that measures the earthing resistance of an installation in ohms. It is used to document the resistance value in commissioning measurements and periodic inspections of the earthing of buildings, transformers, enclosures and lightning rods. This category lists Unit earth meggers that measure with auxiliary stakes in a 3-wire or 4-wire configuration, and clamp-type earthing meggers that measure without driving stakes by clamping around the earthing conductor. Choose the measuring method according to the structure of the earthing system and whether the site allows stakes to be driven, the measuring range and resolution according to the expected resistance value, and the recording memory and the stakes and cable set supplied with the device according to the job. Clamp-type measurement gives a result only in systems where several earth electrodes are connected to each other and the measuring current can complete its circuit; for a single earth electrode not connected to another earthing, the stake method is required. An earth megger does not replace an insulation megger, which measures the insulation resistance of cables and windings at the megohm level.

Earthing Measuring Instruments Selection Guide: Technical Criteria & Application Standards