Protective conductor resistance measurement

Certain device designs need a housing of metal. However, the properties of a double-reinforced insulation to live parts cannot always be achieved. Owing to their construction, heaters, in particular, can largely only be insulated on a basic level. However, the process of a basic insulation requires a reliable protective conductor connection, which influences the possible contact voltages if there is a fault.  

In the case of devices with a protective conductor connection (protection class I), therefore, the corresponding protective conductor resistance must be measured. In this process, the resistance of the system is determined between the metal enclosure and the protective conductor connection at different points with a test current of the order of amperes. In most cases, the normative resistance is less than one ohm and must not be exceeded.