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Unread May 5th, 2015, 01:04 PM   #1
Mike_RH
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FactoryTalk View SE

Hi Gents,

I am having a discussion with a coworker about tags in FT SE, or ME for that matter.
The PLC is ControlLogix, the question is when to create a HMI tag database and when to directly reference the tag in the device.

I prefer using the HMI database, as then if I need to make a change, there is only one to make.
My coworker prefers to directly reference the device when adding the object/animation on the screen.

Any opinions / advice on this?
Or does it really come down to personal preference?
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Unread May 5th, 2015, 01:54 PM   #2
rdrast
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Direct referencing sounds nice and all, but it is a nightmare in larger systems.
It is also a complete nightmare if you did such a good job, that management want's you to duplicate it on several machines.

Using HMI tags, you can do that easily with a quick find and replace on the tag database.
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Unread May 5th, 2015, 02:05 PM   #3
arlenjacobs
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(1) For FTView SE, you need HMI tags for alarms.
(2) With HMI tags, you can export the list to a CSV file (for various edits/changes)
(3) The speed is different.


HMI tags are 2x slower for READ updates compared to direct reference. Tag WRITES make no difference, they both go through as fast as possible.

In FTView, all of the tag updates are set by the display properties. If the update rate is set at 1 second then that display will poll for updates every 1 second.
When you use direct references, your data actually updates every ~1 second.
When you use HMI tags, your data actually updates every ~2 seconds.

5 second display update rate gives you a 10 second update with HMI tags.
Try it out; use a millisecond timer as your data to show the updates.

Maybe it's different in version 8, but in past versions that is what I saw.
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Unread May 5th, 2015, 03:33 PM   #4
Geospark
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Quote:
Originally Posted by Mike_RH
...does it really come down to personal preference?
To some degree, yes. But there are factors that should be weighed up before deciding which to use.

HMI tags - Pros...

Template applications can use HMI tags for relative ease of portability
You can implement folder structures for tag access
Use more descriptive tag names
Maintenance/Usability time will be reduced for editing
They have scaling, offset and retentive features
Tag value can be used to trigger alarms
Analog and Digital tags can have alarm conditions

HMI tags - Cons...

5000 tag creation limit
Tags must be resolved in the tag database before communicating with controller
HMI tag database must be exported/imported before a display can be used in another application
Initial tag loads are slow as the tags need to be cached
HMI tags are at a minimum 1 second slower than Direct Referenced tags for both read and write tag data updates (tag database must be accessed for both)
Extra tag description information consumes more memory
Retentive tags consume more memory
Each HMI tag used will typically consume 2.9KB of RAM

Direct Reference tags - Pros...

There is no Direct Reference tag creation limit
Direct Reference tags communicate directly with the controller and avoid the HMI tag database
Direct Reference tags are refreshed much quicker and can be used on displays that require increased performance
Direct Reference tags can be directly linked to objects on displays
Displays using only Direct Reference tags can easily be ported to applications with the same shortcut name
Each Direct Reference tag used will typically only consume 1.1KB of RAM

Direct Reference tags - Cons...

Less descriptive tag names
No tag folders available for structured tag access
No scaling, offset or retentive features - must be done in controller or module
Maintenance/Usability time is increased for edits

Quote:
Originally Posted by Mike_RH
...I prefer using the HMI database, as then if I need to make a change, there is only one to make...
One of the advantages of HMI tags is the Maintenance/Usability time saved because they facilitate a single point edit. This is probably why you prefer them.

Quote:
Originally Posted by Mike_RH
...My coworker prefers to directly reference the device when adding the object/animation on the screen...
One of the advantages of Direct Reference tags is that they can be assigned directly to objects on displays. This is probably why your co-worker prefers them.

So neither of you is really "right" or "wrong" in what you have chosen to use. Ye are using the best tag options to suit your given needs. But whether one should sway all one way or the other, is another matter. Depending on the application, you may need a mix of both, to some degree.

If you need to leverage the advantages that HMI tags provide, such as alarming, descriptive tag names and folders, retention, repeatability, etc., then chose them.

If you need to leverage the advantages that Direct Reference tags provide, such as quicker tag data updates, direct object linking, memory savings, etc., then chose them.

Regards,
George
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Unread May 5th, 2015, 03:43 PM   #5
Mike_RH
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Thanks for the feedback information.
Rdast - your comments mirror my own feelings - maintenance headaches later for direct references.
ArlenJacobs - I did not know of the timing difference direct reference / HMI tags. That is significant. I am going to give it a test to see if it is the same in V8.
Geospark - Great summary, thanks

My coworker and I are now off for a brown pop to continue the discussion!
Thanks to all again.
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Unread May 5th, 2015, 04:16 PM   #6
Geospark
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On the HMI tags refresh delay issue...

One progressive feature that was introduced primarily to improve access speeds to the HMI tag database was the move, at FactoryTalk View SE/ME v6.1, from the older WATCOM ODBC tag database to the newer and faster Microsoft SQL Server 2008 R2 Express tag database (using instance FTVIEWx64TagDB).

G.
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Unread May 6th, 2015, 07:58 AM   #7
rdrast
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@Geospark: What 5000 tag limit for HMI tags?
I'm looking at an application right now with 33,123 HMI tags defined.
And I have no speed issues, most of my displays are set to 0.25 or 0.1 second updates, with no issues.
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Unread May 6th, 2015, 02:31 PM   #8
arlenjacobs
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FTView is a display limited product, not tag limited; you pay for the number of displays that you use. But there are limits to the number of alarm tags and the number of tags within a single display.

FTView SE max 40k alarm tags, max 3k tags per display
FTView ME & PanelView Plus max 5k alarm tags, max 1k tags per display


Yes, you can increase the display update rate to get around the HMI tag speed issue. That will increase the Data server loading, or on a PVP it just uses more memory and CPU. In all cases it doubles the network traffic and doubles the loading on the controller.

HMI tag update rates are still an issue in FTView 8.0
What are the actual update rates during runtime?
Below is a display with a 5 second update rate, you see the HMI tag will always be one update behind.
HMItags.jpg

If your system can handle a little more traffic, yes it's worth using HMI tags for all the nice editing/maintenance ease.

Last edited by arlenjacobs; May 6th, 2015 at 02:33 PM. Reason: Image
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Unread May 6th, 2015, 06:39 PM   #9
Geospark
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Quote:
Originally Posted by arlenjacobs
FTView is a display limited product, not tag limited; you pay for the number of displays that you use...
Yes, that's correct. I've previously outlined as such here...

FactoryTalk View Options...

Quote:
Originally Posted by rdrast
@Geospark: What 5000 tag limit for HMI tags?...
Sorry, yes I should have stated that the 5000 tag limit was a HMI alarm tag limit for a project and that it was for ME only. Mike had primarily asked about SE, and then added ME to the question as well. I should have differentiated. I should, and normally do, give much greater detail, but I threw that together as quickly as I could as I was in a bit of a hurry.

The limits that arlenjacobs has listed are correct.

Also, within the 40,000 alarm tags for SE, 10,000 of those can be analog tags.

The per Display limit is defined more as a "connections" limit than a tag limit.
For instance, an expression referencing a tag can count against the connections limit.

As can other references...

Observing tag-related limits:

A graphic display can contain up to a total of 1000 ME, or 3000 SE connections, whether they originate from the expressions or the tags.

Each expression associated with an object is counted as one connection regardless of the number of tags in the expression.
Each animation of an object (except the Touch animation) is counted as one connection.
Each connection in the Connections property of an object that is linked to a tag is counted as one connection.
Each pen configured in a Trend object is counted as one connection.
Duplicate references of the same expression or tag connection are counted as additional connections.

For example, one SE display can contain up to 3000 numeric inputs, even if all numeric input objects refer to the same tag, they all count against the connection limit.

Note: Tags associated with embedded variables do not count towards the limit.

The slower (1 second) delays observed using HMI tags instead of Direct Reference tags were more of an issue with the older WATCOM Tag Database. v6.10 and above do show marked signs of improvement while using the newer SQL Server Tag Database. That was sort of why I mentioned it. But because HMI tags still have to be resolved against the Database before their data can be communicated, they will always be somewhat slower than Direct Referenced tags.

rdrast,

If your application is running on the older WATCOM Database, then a rule of thumb is to add 1 second (in your head) to the "Maximum Tag Update Rate" for the Display. So an update rate of 1 second may typically be up to 2 seconds for HMI tags referenced on that Display. This is supposed to give you a rough idea of the likely delays you "may" experience. It's not a hard and fast rule. Some applications using HMI tags can perform very well. It also has a lot to do with size and complexity of the application and its Displays, the software version, old or new Tag Database, terminal type or computer the application is running on, not to mention the communication network performance.

HMI tags have one more hop to make, the database. So they are inherently slower than Direct Referenced tags. How much slower varies, and if you are lucky, or have designed it well, you hopefully won't really notice it.

Regards,
George
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