What is the best solution to interface a large number of analog inputs

Paully's5.0 said:

Pardon my ignorance on the task at hand, but why would you bother looking for a multiplexer with Ethernet/IP to a PLC? Plenty of bandwidth over Ethernet to read individual IO. I can only assume its a $$$ issue?

I'm with kolyur, use a remote IO rack and load it with RTD cards. Wago would another alternative.

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Thanks for your response.
The reason is mainly because of cost implications.
RTD cards and individual analog cards cost alot. While a MUX can bring this down. The other reason is, it's quite a large number of temp transmitters. A total of 320 transmitters divided into 4 remote drops amounting to 80 in each drop. The remote drops have a number of DI and DO.
Therefore there is a lot of cards if I went individual input into the PLC.

Currently I have something like this:
MainPanel (Compact logix - L33ER)---
RIO1(Point IO)DI/DO/80AI---
RIO2(Point IO)DI/DO/80AI---
RIO3(Point IO)DI/DO/80AI---
RIO4(Point IO)DI/DO/80AI.

Reason I am looking for Ethernet/IP is because Rockwell is not so modbus friendly for instance and a modbus card could cost a bit. Also I am stuck with compact logix. So I am trying to see what can be a best fit.
Please share your thoughts?

Really.. how can I connect 80 such temp transmitters per remote drop in the best way possible??? As I mentioned before this PID is slow and so I can afford to have the values update in seconds rather than a live value as the temp change is relatively slow in this process.
Just cant seem to find a fit for this requirement based on the best cost possible.

Thanks

I'm not sure you'll find what you are looking for at a low cost and over Ethernet.

I came across this 6 channel over Ethernet, but @ $115/point it's still costly. Don't forget to include the additional costs of the additional networking, control wiring (more fusing) and increased panel size.

Automation Direct (Beckhoff/Wago)has an RTD IO card costing $67/point. I don't think they have an Ethernet/IP coupler but pricing would be similar to Beckhoff/Wago which offer Ethernet/IP

Best of luck in your search.

Are the temp transmitters 4-20MA?

Look at Opto22 for Ethernet/IP remote IO.
Each Remote rack could use 3 32channel +/-20MA cards
http://opto22.com/site/pr_details.aspx?cid=1&item=SNAP-AIMA-32

Or 2 32 channel plus 2 8channel cards. You can also get DI/DO.

vigz, I replaced a whole MUX system on Christmas Island ate the power station during the full automation of the power station late nineties - the MUXers kept failing. Response was slow - too late - oil pressure went down - diesel generator stuffed - buggered and all those things. $250k to rebuild it. I will never use MUXers after that experience - I did not use them anyway - someone else did. They got sued for heaps. It does not pay to go cheap. Omron have some quite inexpensive analogues that work on Ethernet IP. Using them at the moment. RIO is really expensive because it is proprietary.

thanks for your responses. Some of those hardware not even heard of. Appreciate your responses. Assessing how I can put together with the options I have received here.

vigz said:

http://www.ifm.com/products/us/ds/AL1020.htm

Its a IO Link master module, there is a variety of it, and uses the IO link protocol which is quite similar to Profibus from what I understand. It can be used to configure instruments as it is bi-directional. A little bit of an overkill for my application unless I find the right architecture.

Hope this helps.

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I don't think the ifm device does what you think it does.
Your temperature probes would need to be IO-link devices that transmit their process data on IO-link, and you would only be able to hook up one to each port.

Are your RTD's converted to 4-20ma (Wago 750-496) or do you need an RTD input module (Wago 750-451)?
I can't see how a MUX would be much cheaper than "proper" Ethernet or Devicenet Remote IO, and certainly not after you account for programming and troubleshooting time.

BobB said:

vigz, I replaced a whole MUX system on Christmas Island ate the power station during the full automation of the power station late nineties - the MUXers kept failing. Response was slow - too late - oil pressure went down - diesel generator stuffed - buggered and all those things. $250k to rebuild it. I will never use MUXers after that experience - I did not use them anyway - someone else did. They got sued for heaps. It does not pay to go cheap. Omron have some quite inexpensive analogues that work on Ethernet IP. Using them at the moment. RIO is really expensive because it is proprietary.

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That sounds intense.
Did the manufacturer get sued? I have heard of such failures but in the recent past it would be hopeful that these MUX would be robust yea?
I guess I will have to price up the RIO option which will be quite a large panel and excess cost.

8ch AI cost NZD1800 (no 16ch in the point IO),
16ch MUX cost 1100.

so,
I need 10 8ch cards ~ $18000
or
5 MUX ~$5500. (with some networking costs)

There are few options I have discussed with colleagues as well. Will see what we go with. Will keep posted.

cleeton said:

I don't think the ifm device does what you think it does.
Your temperature probes would need to be IO-link devices that transmit their process data on IO-link, and you would only be able to hook up one to each port.

Are your RTD's converted to 4-20ma (Wago 750-496) or do you need an RTD input module (Wago 750-451)?
I can't see how a MUX would be much cheaper than "proper" Ethernet or Devicenet Remote IO, and certainly not after you account for programming and troubleshooting time.

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Agreed.
I talked to the iFM vendor and they did mention I need a converter for every transmitter.
This may not work.

This is the latest consideration at the office;
http://www.intech.co.nz/products/remotestations/2400-a16.html
The net version says it can do Ethernet comms.
This seems like the favorite contender.

vigz said:

Agreed.
I talked to the iFM vendor and they did mention I need a converter for every transmitter.
This may not work.

This is the latest consideration at the office;
http://www.intech.co.nz/products/remotestations/2400-a16.html
The net version says it can do Ethernet comms.
This seems like the favorite contender.

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It does Modbus TCP over Ethernet which is not really supported natively on compactlogix. Ethernet/IP and Ethernet TCP/IP are NOT the same thing.

This really comes down to how much your time is worth.
If your time is expensive, get Allen-Bradly, configure with a few clicks in Logix IDE.
If your time is moderately valuable get 3rd party Etherent/IP (Wago, Beckhoff, Turck), deal with mapping registers, third party config utilities and Generic Ethernet/IP device configuration.
If your time is worthless keep looking at the **** your coming up with.

The Omron Ethernet IP 8 channel analogue modules are about $550 and you could probably negotiate a discount - I do not pay that. The Ethernet IP coupler module is about $420 - negotiate discount again. I have 26 digital I/O modules on one coupler - 2 x 16 channle 4-20ma inputs, 4 x 4 channel 4-20ma output modules on another coupler and mixed I/O on 2 other couplers. The first 2 are in the switchboard and the others are remote. I did not pay the prices above as I am an Omron SI and have a fixed discount in place. I would definitely not be using MUXers! Too much pain and time involved fiddling about. By the way, when you go over a certain amount of I/O the back bus on the Omron units runs out of power supply - as with all these things. Simple insertion of a power coupler (inexpensive) in the back plane and all is good. I had to use power couplers in the first coupler configuration - no issues.

cleeton said:

It does Modbus TCP over Ethernet which is not really supported natively on compactlogix. Ethernet/IP and Ethernet TCP/IP are NOT the same thing.

This really comes down to how much your time is worth.
If your time is expensive, get Allen-Bradly, configure with a few clicks in Logix IDE.
If your time is moderately valuable get 3rd party Etherent/IP (Wago, Beckhoff, Turck), deal with mapping registers, third party config utilities and Generic Ethernet/IP device configuration.
If your time is worthless keep looking at the **** your coming up with.

Click to expand...

Good point, I have no idea what to say to that except its a matter of compromise.

Anyways, I have got some good suggestions and opinions on this thread and some hardware that I have no even heard of and not even sure if its easily available in this part of the world.

Thanks

There is a lot of info in this thread and at this point I'm confused on what you actually need. I see mention of RTD and 4-20ma. What do you actually need? And I see a pricing structure for ten 8pt cards = $18000

Have you looked at Automation Direct products? I'm not sure what shipping would be like and their support hours are going to be off from yours, but so far I've not had a reason to buy PLC's from anyone else.

If you need 4 drops of 80 inputs you could go with something like a Productivity 2000 system to build 1 local and 3 remote racks;

(4) Power supply, CPU (1 local and 3 remote), (4) 7 slot base, (20) 16pt 0-20ma cards (5 per rack), all associated cabling and ZipLink blocks = $6162 USD (less than $20 per point).

The P2K system is pretty slick. You have one local rack and assign up to 99 remote racks. All of the addressing is done in the software as if everything was local, it's ultra transparent to the programmer. You could then connect the local rack to your AB controller via MODBUS TCP or RTU (over the build in RS485 2 wire port).

[edit] the pricing on those is for the 13bit cards. If you need higher resolution, they have a 16bit card for ~$60 more per card.

Also, it's unclear if you need RTD or 0-20ma. I see you're using PT100 sensors, but I'm not sure if you already have 0-20ma senders or if those still need purchased? If you need direct RTD input, they have 6ch 16bit cards for $325/ea, you would need 14 per rack. It drives the cost up a ton, right around $5k per rack, but it would save the cost of buying 0-20ma transmitters. [/edit]

If I were your customer, I would not accept any kind of "multiplexing" of analog signals.

Go for Ethernet/IP modules with analog i/o, but from another less-expensive-than-AB brand.
For example:
Omron NX.
Beckhoff.
Think about it, what is the use of an open standard if you still only consider one brand.

JesperMP said:

If I were your customer, I would not accept any kind of "multiplexing" of analog signals.

Go for Ethernet/IP modules with analog i/o, but from another less-expensive-than-AB brand.
For example:
Omron NX.
Beckhoff.
Think about it, what is the use of an open standard if you still only consider one brand.

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I'd second this. I've used both Beckhoff and Omron NX I/O. I currently use Beckhoff for temperature monitoring on our kilns. The units are great and I've had very little problems. The problems I've had were initial setup and the US tech support staff was very good with helping me work through them.

The nice thing about the Omron NX is you'd be looking at enough $$ when all is said and done, that the distributor would probably throw in Sysmac Studio software for free.

But when all is said and done, its about the support available to you in your area, price isn't everything at 3am when something stops working.