Monitoring Device and Method of Monitoring an Impedance of a Protective Conductor, and Charging Control Unit

A monitoring device for monitoring an impedance of a protective conductor, comprising:

• a first input terminal;
• a second input terminal;
• a first resistor;
• a second resistor having a resistance value which corresponds to a threshold value for the impedance of the protective conductor;
• a third resistor;
• a bridge diode;
• a first node between the first resistor and the second resistor;
• a second node between the third resistor and the bridge diode;
• a first voltage divider for connection to a voltage source and connected:
• (a) to the first resistor and the second resistor in a series, and
• (b) between the first input terminal and the second input terminal;
• a second voltage divider:
• (a) connected in a series to a first end of the third resistor and the bridge diode,
• (b) connected to the first end of the third resistor and the first resistor,
• (c) connected to a second end of the third resistor to the protective conductor;
• and
• a measuring device:
• (a) for detecting a bridge voltage between the first node and the second node if the impedance of the protective conductor is greater than the value of the second resistor, and
• (b) connected between the first node and the second node.