The WITT CM 4 is a self-resetting cable monitoring device for the detection of cable faults.
The device is used to monitor the insulation of cable systems in DC systems. The cable monitoring device allows both standard insulation monitoring between conductor and shield, shield and earth, as well as additional monitoring of the shield for interruptions.
Potential-free relay contacts are available for the message. The device is built into a plastic housing that can be mounted on a wall or top hat rail.
The optional external display unit (bar graph) enables the display of limit values and insulation values.
The insulation sections to be monitored are connected in parallel to achieve defined conditions. These resistors are dimensioned in such a way that the nominal screen voltage is limited to approx. 40 V and the measuring current through the screen to approx. 1 mA.
An interruption in the screen leads to the message earth fault (screen – earth) or internal short (conductor – screen). If the web tension fails, this is indicated on a potential-free contact.