Why would grounding the common attenuate noise? If I have an isolated 24VDC power supply I can only see grounding the common as introducing noise into the system. We have our unit installed at a factory that reads our signal with an Analog input module. There is some noise on the line and i believe its because they ground the 0VDC to the PLC. Does anyone have experience with this? Thanks, Omer Peleg DTI