Control device for electric load

The device has a control device mass (18) connected with a mass (4) of a voltage source (2) over a bulk entrance. A voltage monitor device monitors electric potential of the control device mass. A reference mass entrance is different from the bulk entrance. A potential divider is provided with a base point, a tapping point and a head point. The base point is electrically connected with the reference mass entrance and the voltage monitor device such that the electric potential of the control device mass is monitored by comparison with potential of the tapping point.