I currently went to a site to troubleshoot some signal spike issue on their gas plant. What I found is three ground bar in the PLC cabinet. equipemnt ground bar, DC negative ground bar, and isolated instrument ground bar. and they put a jumper to jump negative ground bar to equipment ground bar. I was wondering shouldn't be jump DC negative ground bar to isolated instr ground bar to avoid nosie for the 24vdc signal more make sense. Please let me know where the negative ground bar should connected to?