Transfer Analog signals from remote I/O to DCS

I would like to enquire for a product as a solution for our on-going project.

We need to transfer some analogue signals (QTY:08 / 4-20mA ) from Remote I/O cabinet to our DCS System (Hardwired).

We have signals in an output (4-20 mA) form and now we are looking for a multiplexer and Demux system to transfer data using twisted pair.

The length between Point A to Point B is almost 1.5 KM.

As requested by customer, we can’t offer them any wireless solution. Can you kindly recommend us which multiplexer system can be used in this situation to transfer noise free data.

Your immediate reply will be highly appreciated.

I'm not fully understanding what you're trying to do with the signals, but a common approach is to have a remote analog input card in the field that would receive the signals, digitize them and send over EtherNet, DeviceNet, PROFIBUS, etc.

If I was given the information above, I would utilize PointIO from Rockwell and read the signals over EtherNet (however you want to bring it over; I'm thinking fiber optic would be needed for such distance).

Cheers,
Vlad

I would agree with Vlad. The network cable should be long, not the signal wires.


If you're using Remote IO, it is usually placed near to the IO. You can then do your communication via fiber optic Ethernet, over some IO network (Profinet, EthernetIP, ModbusTCP, etc), or a fieldbus that supports fiber.

I've used these:
https://www.netsys-direct.com/colle...ernet-extender-with-remote-power-nv-202rpekit

Then whatever ethernet based remote IO

For that kind of distance I would recommend you use Profibus PA, which can power the devices. You need a plc with analog output cards to connect to the DCS. Then the pkc needs a Profibus DP or Profinet scanner. It be required either a DP/PA converter or Profinet/PA gateway. Profibus PA is slow, only 31.25 kbaud, but normally this is OK on many process applications. A bit of logic that reads the PA inputs and maps them to the analog output of the PLC should be good for this solution.

Hello Everyone!

Thanks all for your immediate responses.

The Scenario is ; Client is saying me to fetch data from a remote I/O cabinet having Siemens remote Analog output module.

He will configure the 4-20 mA signals to that RIO Cabinet (Having an analog output Card). This means from there, I am required to take that signal to my PLC station(Siemens Analog input cards) as hardwired (Distance is about 1.5 Km). As the distance is too much i can not use multi-core hardwired cable.

I searched on Internet there is a multiplexer system which take 4-8 analog input signals, transfer that to a twisted pair FO cable and on the other end we can use a demultiplexer to get those 4-8 Analog signals. Does any one know about this multiplexer and demultiplexer system? Or any other solution so that i can transfer those signals without any signal data losses.

Immediate response will highly be apreciated

Vlad Romanov said:

I'm not fully understanding what you're trying to do with the signals, but a common approach is to have a remote analog input card in the field that would receive the signals, digitize them and send over EtherNet, DeviceNet, PROFIBUS, etc.

If I was given the information above, I would utilize PointIO from Rockwell and read the signals over EtherNet (however you want to bring it over; I'm thinking fiber optic would be needed for such distance).

Cheers,
Vlad

Click to expand...

Thanks for your response; what I want is to take those analogue output signals (from Siemens Analog output card at field) and communicate it with my SCADA (Spare Siemens Analog input cards are present). So in overall , just to take that output signals and configure those in my analogue input Card. Issue: The distance is 1.5 Km and signal will be lost if take signals as hardwired.

K.Anwar said:

The Scenario is ; Client is saying me to fetch data from a remote I/O cabinet having Siemens remote Analog output module.

Click to expand...

I'm going to be frank, as far as I'm concerned, your client is asking you to do something dumb. I guess I could be wrong.



You'll probably spend enough money to buy & troubleshoot the HW multiplexer system, that it would just make sense to put a remote IO rack in their panel, and run the remote IO back over the FO cable instead as Profinet (or Profibus, if you must). The actual Hard Wired part would only be a few feet long, and the rest is a robust and practically noise proof Ethernet solution.



Another potential option would be to use some kind of gateway (PN/PN coupler, anybus, whatever) to send IO data directly from one PLC to the other, without messing about with hardwiring IO signals.

MK42, I agree with your solution. I misunderstood the original explanation

mk42 said:

I'm going to be frank, as far as I'm concerned, your client is asking you to do something dumb. I guess I could be wrong.



You'll probably spend enough money to buy & troubleshoot the HW multiplexer system, that it would just make sense to put a remote IO rack in their panel, and run the remote IO back over the FO cable instead as Profinet (or Profibus, if you must). The actual Hard Wired part would only be a few feet long, and the rest is a robust and practically noise proof Ethernet solution.



Another potential option would be to use some kind of gateway (PN/PN coupler, anybus, whatever) to send IO data directly from one PLC to the other, without messing about with hardwiring IO signals.

Click to expand...

Dear mk,

That could be a dumb thing for us but as you know, we can only propose them a solution. Actually, There are two Separate plants that's why client doesn't want us to give any accessibility to one another (Any CPU to CPU connectivity over same ethernet network). This is the reason he is saying that he will generate output from his side and then we may fetch data to our PLC. So there will be no connectivity between two PLCs but we will have data on our side.

it would be a great help if you have any idea about peer-to-peer communication? kindly look below the attachment, this is the solution i want.

K.Anwar said:

So there will be no connectivity between two PLCs but we will have data on our side.

it would be a great help if you have any idea about peer-to-peer communication?

Click to expand...

Remote IO hard wired into their IO would provide no connectivity between the two CPUs, so it could qualify. However, you would have a network connection from one plant to the other, even if it didn't allow communication between the PLCs, which is probably the real concern.



A Peer to peer solution could potentially work. The picture you put in seems promising, but I don't know what product that is to know further. I've never used something like that.

Phoenix also makes something that may be usable...

https://www.phoenixcontact.com/onli...08-13-03/9fde7442-b35f-4ff7-aa98-47e86495ed41

I've used something similar (although it would have been much higher bandwidth) and the cables must be really good and not jump through junction boxes, etc... The distance was about 800 meters and it wouldn't work, but these were 40 to 50 year old cables with a few junction boxes in between so it didn't surprise me in the end.

What PLC's are being used here? Can you install a junction box with power at about halfway between both of the PLC's? If they're both Siemens, I was thinking that you could install a profibus link and stick a DP coupler in the middle which doesn't let one company access to the other side. Another option could be to set up two gateways which will too insulate the two networks whilst being slightly easier to do than wire signals.

And the reason I mention this is that I can almost guarantee you that two months after you've completed the hard wiring, someone is going to come back to you and ask for an awful lot more signals.