The GM420 is a relay that monitors the integrity of the ground conductor (PE) or ground loop for permanently installed equipment in AC electrical systems. The ground conductor is our life guarantee. Therefore, this device's main function is to monitor the resistance, continuity and connection of the conductor that acts as a protective ground.
 
The GM420 measures the resistance of the ground circuit between the equipment grounding conductor (PE conductor) and the
metal structure of electrical loads (for example, the casing of a motor) by laying a power cable
return lands to the same GM420; this in order to ensure a properly connected grounding
and high quality. As it is designed for fixed equipment we can usually find it inside the
industrial plants.
 
The GM420 is a supervisor that, in addition to monitoring the integrity of the PE conductor with motors or electrical loads,
You can also check the electrical resistance of the ground connection between different points, in order to determine the
ensure equipotential connection in industrial plants.
 
The equipment's digital display shows the ground loop resistance in real time. The GM420 also monitors
any transient voltage that may occur between the two monitoring points.