u/Accomplished-Set4175

The machine is a kiheung U'3 milling machine with a heidenhain TNC154 PLC and I'm trying to solve the DC voltage missing symptom. When I measure the 24 volts going into the plc it always measures good in both the power input connections. At a terminal strip inside the console however there's 24 volts on 1 connection and only 8 on another. There are 3 separate grounds here PE, OV and OVS. The reduced 24 volts measures ok to only OVS only but not OV. Why are there 3 grounds? And is it OK to jumper them, temporarily to each other? Thanks. To 0V shows a voltage with respect to PE. I'm sure 0V and OVS should both be at 0 in respect to PE.