G
I'm going to use 1746-NI4 analog input modules with an AB SLC-5/04 to monitor 0-10 VDC signals from a few drives and transducers. No problem up to here, but the manual mentions that the module's 4 channels are not individually isolated, and that analog commons are internally interconnected (each channel has IN+, IN- and ANL COM terminals); however, it does mention that double-ended differential inputs can use the IN+ and IN- terminals, as long as they remain within +/- 20 volts of COMMON to insure proper operation. My analog signals will not necesarily share or have the same common or negative reference, so I'm a little confused and concerned on the "not individually isolated" spec on the module's manual. Does it mean that I can safely connect differential signals from dissimilar equipment into the module, as long as I ensure that the +/- 20 volt restriction is met? Or does it mean that a spike or short on one of the inputs can damage equipment connected to the other channels? Or, both of the above? Also, if all inputs are differential and use the IN+ and IN- terminals, can I leave the ANL COM terminals unwired? Any light shed on these matter will be greatly appreciated. Regards, Bob Gantt