GordoP

Ok, so let's say we have a AB SLC 500 with a 1746-NI4 Analog Input Module and no other input or output modules installed. The manual shows the input module input terminals are as attached. Can I connect channels 1, and 2 to different parts of the same circuit that are at different potentials (i.e. would the picture enclosed with the original post work?) (I understand maximum input voltages, etc, the drawing is just for concept.) Thank you, Gord

It could be different ones depending on the location. One I do know of is an AB SLC500 based system and one of their standard I/O cards, though I don't know the exact model. The SLC 500 Analogue Input Module manual I was reading appears to suggest the whole series have the same interface. Will different manufacturers not always have IN+, IN-, COM? And if so, do some have single-ended inputs only? Thanks again! Gord

I'm sure this is a very basic question, rest assured I'm not in the PLC business, just wondering about applying one. The PLC manual says common terminals are common and the drawing enclosed shows them not used. There is also IN + and IN - 1) Are the “In-” terminals effectively isolated from one another so I can connect channel 1, 2, and 3 to different parts of the same circuit that are at different potentials (i.e. would the enclosed picture work?) (I understand maximum input voltages, etc, the drawing is just for concept.) 2) Curious, what are Common terminals used for then? Thanks for your assistance! Gord