Contrologix 1756-IF16 analog input card

I have a controllogix Plc with a 1756-IF16 analog input card. There are 8 input cables and they only have 2 wires. Then there is a jumper over to the other terminal I think it is rtn. I have to add 3 more analog inputs. Do I need to get another analog input card for this type setup

If each cable is connected to 2 input points (example: IN-0 & IN-1), then the module is setup for differential inputs and you therefore don't have a spare channel available. It sounds as though your module is wired for 8 differential current inputs, based upon your description of a jumper to the RTN terminals.

Have you checked to make sure that all 8 cables are actually connected to field devices, rather than merely to a control panel terminal board?

They are all being used. Those 8 are for a different type setup. I have to add 3 analog inputs for scales. 1 analog input for each scale. Do I wire it up in the same way?

jtashaffer said:

They are all being used. Those 8 are for a different type setup. I have to add 3 analog inputs for scales. 1 analog input for each scale. Do I wire it up in the same way?

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You could use single ended inputs for most instruments. You only need to set an analog input module up for differential inputs when your instrument outputs a signal that crosses from negative to positive.

Assuming that your scales have a 4 to 20 mA output, which is typical, then you could use a 1756-IF16 module to facilitate 16 inputs.

The wiring diagrams for that module are shown in this PDF document.