Tags versus I/O

  • Thread starter Adolfo Jimmy Saldivias Valarezo
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Adolfo Jimmy Saldivias Valarezo

Dear List:

I am evaluating several Scada packages for a project in a mining concern. I have found that suppliers like Intellution and National
Instruments quote their products based on I/O count.

Wonderware quotes their products based on "tags".

Could anyone give me an advice on how to equate tags and I/O count, so we can compare "apples with apples" for this application.

Also, please forgive me if I am asking a forbidden subject: pricing info.

But after spending what I consider too much time in the internet, I found published prices for Intellution and Lookout but not for Wonderware. I think I will try to make better use of my time by
asking directly to you about this.

Is there any place in the web where I can find pricing information on Wonderware? I have checked every page of the listed distributor on the wonderware site but none of them have pricing info. Please contact me directly about this <[email protected]>.

I have also requested quotation from my nearest distributor but that usually take a long while to get an answer.

Jimmy Saldivias

Anthony Kerstens

I/O would be what is communicated with external devices like PLC's. In Wonderware, I/O is a subset of tags. That is, for every I/O point
and register, there must be a tag. Tags in Wonderware are also used for internal discrete/analog values, pointers, special constructs, etc.

So, in Wonderware, if you have a 64k tag license, the total number of your I/O points and registers, internal discrete/analog values, pointers, special constructs, etc. is 64k. Other competing products don't limit the number of internal tags you can set up, only the I/O communicated to the external devices.

Anthony Kerstens P.Eng.

Dittrich, Rodolfo

Jimmy, the biggest product of wonderware, that is the license with 64Ktags is between 10000U$D and 12000U$D, depending on the country taxes. Trying to help to your decision, remember that every variable asociated with and input or an output counts for the quantity of tags, the same is if you declare an internal variable not associated with inputs or outputs. For wonderware every tag (external or internal) counts.

Probably intellution have an fixed quantity for tags that are not associated with external inputs or output.

Note that if you are using Intellution, the restriction on physical tag count can become a real headache as you need to push more and more data from the PLC to the HMI. While it is true that you aren't limited on internal variables, you can't do much with them without process info to work with.

Paul T

Anthony Kerstens

So, if WW's big package is 64k tags total including I/O, what would Intellution's comparable "big" package be?

Anthony Kerstens P.Eng.

Most SCADA apps charge by I/O consumed during creation of an application. In other words, if you have one physical I/O point, then use that I/O point to create statistical figures "Run Time", "Volumes Consumed" etc etc etc, most of these companies will charge you for each and every "tag" you've consumed.

Wizcon (www.emation.com) on the other hand, charges you for physical I/O only. For example, I've just created a VERY complex system in Wizcon with 1,000 physical I/O points, but a total of nearly 10,000 total tags. Almost 9,000 tags were consumed to hold statistical and operational information such as Run Times, Pumped Volumes, Pump Manufacturer, Date Installed, Scheduled Maintenance Date etc etc etc..

Wizcon charged me for 1,000 tags only.
If I'd done this project under many of the other apps, they'd have sent me a HUGE invoice !!!

Suggest you give them a look ,,,, or drop me a note.

Mark Hill, President - Intelligent SCADA Solutions
[email protected]

John Boone Pooler

Jimmy Saldivias & "the List",

With regards to how you should compare "I/O" based HMI packages and "Tag" based HMI packages... be very careful.

I have had an opportunity to work for a couple companies which offer the software you are considering.

Packages that are "Tag" based are easy to understand. If you want to see a value (or to be able to write a value to the field) you need a TAG. End of story.

With packages that are I/O based, it is easy to ASSUME that if you don't have a wire connected to a field instrument (valve, transmitter, solenoid, motor, etc.) it doesn't count. BUT this is WRONG!

The easiest way (or at least the one that I use to illustrate the point to customers) it to place an imaginary "wall" between the computer and the field controller (PLC, Analyzer, multi-loop
controller, etc.). Any information that must pass through the wall, either as information coming from the field, or data that you are
trying to write to the field controller, counts as a "TAG" that will subtract from your Tag Count (or I/O). It DOES NOT matter whether there is a wire attached to the other end, or whether the information resides in an internal register within the PLC (or other field controller). If it passes through the "wall" it will cost you a "tag" (and ultimately money).

The I/O based systems have the ability to generate TAGS that originate within the PC and will never pass through the "wall". These are PC memory based tags and DO NOT count against the
total tag count that you buy.

I hope this is helpful.

John Pooler
There are companies that provide HMI packages with no tag limitation as their standard product. Check out pcvueinc.com or altersys.com
For FIX32, the standard tag counts are 75, 150, 300 and unlimited. I don't know if they'll cut individual deals the way that Wonder will. FIX does provide "analog registers" and "digital registers" that allow you to enter a head-end
address and then use an offset to read or write a bit or register in the PLC. For example, on a machine that I'm working on now we have one FIX digital register tag called "Input" that we use to read all 640 input points on a Fanuc 90/30 PLC. The limitation to this is that AR/DR tags are only polled when you are viewing the screen that they're used on. This means you don't usually want to use them for alarm bits or in scripts, since they don't update all the time.

As long as I'm writing this... we have found the Intellution GE9 ethernet driver to be slow. We have also been able to cause it to stop running (and FIX doesn't notice!) on a regular basis when doing work with both FIX and Versapro. We have
not made a concerted effort to tune the driver, or FIX; if anyone has advice on playing with the FIX SCU and poll setups, or has comments on using FIX32 with GE9, please feel free to drop me a note <g>.

Paul T

Robert Phillips

Lookout by National Instruments (ni.com) does NOT count tags. Only counts I/O from com port.

Robert Phillips
City of Wichita Falls

Patrick Cross

Does anyone have a rule-of-thumb for the ratio of number of tags to physical IO.

I used to estimate on the basis of requiring 5 tags for every physical IO point in a PLC, but as communications technology has improved and more data can be extracted from the PLC, this ratio
has grown to 10:1.

For example on the control system here, which was developed in the last couple of years and runs entirely on ethernet, we have ~40,000 I/O and ~400,000 tags configured in Citect. Whereas in
the mid 90's I was working on Modicon systems which had ~1000 I/O and ~5000 tags configured in the HMI.

Patrick Cross
WMC - Olympic Dam
[email protected]
Opto22 Factory Floor software has no limit on the number of I/O, tagnames or anything and is dirt cheap. Has MMI, OPC server, control, and database connection software all in one package.
I've just finished a small city wide sewage pumping network under Wizcon
Version 7.5 with 1,000 I/O and 10,000 Tags. A ratio of 1:10.
For each physical I/O I required 10 Tags to manipulate data into Run Times, Pumped Volumes, Starts per Day, store maintenance info, and lots of statistical info.

Mark Hill
[email protected]

Anthony Kerstens

There is no hard and fast rule. As you pointed out, communications technology has grown. To the point, I've done SCADA systems that didn't even connect to any kind of physical I/O, just a database.

What's the ratio then, infinity?

Anthony Kerstens P.Eng.
Have you consider RSView32. RSView32 is not dedicated for AB PLC's; but if you are using an AB PLC there are several benefits going with RSView32.
RSView32 is based on tag count (any i/o, register, timer values, counter values that come from the PLC will count against the tag count. Internal registers in RSView32 does not count against your tag count).
RSView32 sales as follows 150, 300, 1500, 5000, 32K and 100K tags. Contact your locat AB distrutor to get prices.