This equipment is specially designed to test the insulation of harnesses that do not have a ground wire mesh (unshielded type). It is used to check that there are no electrical leaks, both between the inner wires and between these wires and the outside.

Since the cables do not have a metallic mesh, the only way to analyze a possible electrical leakage to the outside is to try to generate an electrical jump between the conductive cables
and the vacuum chamber.

The vacuum chamber serves the function of the wire mesh. This ensures that there are no defects in the plastic insulation of the harnesses.