LV DSC 6.1: no tag refresh?

[Chris_From_Brussels]

Hello:
I am using DSC 6.1 with LabVIEW and have the following issue: in the
tag configuration editor I define tags originating from both the
LabVIEW OPC server example (National Instruments.OPCDemo) and the
Kepware simulation server. In the tag monitor tool I can see that all
tags' quality are "good" but only the LabVIEW OPC server example tags
update continuously although other OPC clients software reveals that
the Kepware tags also should change continuously. Now if I stop/start
the tag engine I will get updated values (once) then it stops again
refreshing. I set the deadband to 0 and it does not change anything.
No noticeable tag definition differences between the LabVIEW server
tags and the Kepware tags. Any clue would be much appreciated, thank
you,
Christophe

[Jochen]

Chris,

this is probably related to the deadband setting for your tags in the
tag configuration editor (TCE).
Here is an example:

tag update deadband = 1%
configured tag range = 0 to 100
real value range = 0 to 0.5

In this case the change in the value will never exceed 1% of the
configured range. Thus the engine will only update the tag once after
the engine launch.

Best regards,

Jochen Klier
NI-Germany

[Chris_From_Brussels]

No. Like I wrote, deadband is set at 0%, true range is -100 to +100
and so is the tag range. Sorry...

[Jochen]

Sorry, I was a bit in a rush so I was not attentive enough.
Here is another possible solution:

Change the OPC communication mode in DSC to synchronous communication
for the Kepware server(default is asynchronous and some OPC servers
don't work correctly using this method).
To do this navigate to Tools -> DSC Module -> Advanced -> Server
Browser and click on the button labeled "OPC Client Settings".
Then hit the "View All" button and select the Kepware server from the
list and hit the "Add" button.
Now your OPC server will appear in the Synchronous Communication list.

I hope this helps.

[Chris_From_Brussels]

Thanks Jochen but this does not solve the problem either. Kepware tags
update once then stops until I stop/restart the engine. I have the
same problem with other PCs, whether LabVIEW and Kepware are or not on
the same PC, with LabVIEW 7.1 and DSC 7.1 and having tried different
combination of tag settings. In all cases two other OPC clients
(Schneider and Kepware) show the tags changing.
Maybe you could reproduce the problem by downloading the kepware OPC
server and use the simulation mode they give as default (download is
available at www.kepware.com)
Other than that I am completely clueless,
Thanx,
Chris

[JorisV]

Hi Chris,

I've installed the Kepware OPC server and tried out the simulation
items. At first I had indeed the problem you are refering to in LV DSC
7.0 with LV 7. The tag gets only updated once. You need to change the
deadband but NOT the deadband you can find in: Edit
tag>Operations>engine> Update Deadband. The deadband you have to
change is: for example if you have the item:
Channel_0_User_Defined.Ramp.Ramp1 --> Go to Edit Tags> Connection
>Under I/O Group choose the Edit button> Change the deadband to zero.

Then it works fine.

Regards.

Joris Vanderschrick
Team Leader Application Engineering
NI Belgium

[Chris_From_Brussels]

Thank you very much, Joris. That did the trick. Although I find the
different menus a bit confusing. I thought changing the item property
will take precedence on the group parameter.
Thanx a lot again for your precious support,
Christophe