The MUYA GT5105A is a digital earth (ground) resistance tester used to measure how well a grounding/earthing system conducts fault current safely into the soil. It works with driven test stakes using the standard fall-of-potential method, typically covering a 0-2000 ohm range, and is used when commissioning or periodically re-certifying a building's earthing system. A digital readout replaces the analog needle of older ground testers for faster, clearer results.