Analog output to analog input

[mwiggins]

This may sound foolish, but I need to do this for a temporary fix until we have out PLC network up.

Can I use an Allen Bradley SLC 500 analog output to send an analog input on a PLC 5?

We already have some twisted pair wires pulled and this is a quick solution for passing two temperatures for datalogging.

I could also use two temperature transmitter to send the signals.

Thanks

Marty

 

[Skogsgurra]

I have no specific knowledge about these systems. But as long as the signals are compatible (4-20 mA or 0-10 V etc) I see no problem. You may have to watch out for potential differences in the 0-10V case, not a problem with 4-20 mA signals.

I don't see why it shouldn't work.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[mwiggins]

They are both 4-20mA.

Thanks

 

[waross]

That's the beauty of 4-20 ma systems. It should work fine.
respectfully

 

[HEC]

Just need to be careful with the sink/source of 24VDC!

Mark Hutton

 

[bgood1]

The output of the AB SLC 1747-NO4I is nicely isolated, and connectable to the isolated 1771-IL or to the non-isolated 1771-IFE since it is sink mode and the signal is sourced at the SLC module. I have a numkber of cases where I have done this with incompatible systems. Signal wires shield should be connected to the common negative point of the reading device and open at the source module for best common mode rejection. I am curious as to why not connect them to communicate that info and avoid this?

 

[bgood1]

If you have the wires for the analog you have the means to communicate if both have DH+.

 

[srbelec]

If you decide to use this method, make sure both systems share a common(negative) otherwise you can get some issues even with isolated cards. One solution is to use an Isolator (weidmuller 990880 approx. cost $200)this will allow for both systems to provide loop power and maintain isolation

 

[Sparkylu952]

I read all the responses. I am an expert in this field. If I understand what you are doing, you are sending one temperature to 2 PLCs for some sort of trending are data logging. If the temperature you are measureing is on only one process, then you can send the signal to 2 (or more) inputs. It is an analog current, and when connected in series to multiple devices, the current signal remains the same into each device. If you are using a SLC 500 and a PLC 5, use one 24 VDC power supply, and connect as follows. + 24 VDC from power supply to + on transmitter, - on transmitter to + on PLC 5 analog input, - plc 5 analog input (not tied to power supp;y *important*) to + SLC 500 input, and - SLC 500 analog input to - 24 VDC power supply. You can reverse the PLC input and the SLC input if needed due to location of the power supply. This will provide the EXACT SAME temperature input into each PLC. Contact me if you have questions.