This document describes the features and characteristics of the GMC-I Gossen-Metrawatt GmbH METRISO®1000A insulation tester, including its suitability for measuring insulation resistance in voltage-free devices and systems, insulation testing of earth conductors, protective conductors, and bonding conductors, quick testing with a signal lamp, low impedance measurement, voltage measurement up to 1000V, and minimal use of batteries.