Datalogger error : only numeric variables can be added?

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Jr. Member
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Joined: 20 Apr 2021, 21:10

Datalogger error : only numeric variables can be added?

Post by Charliegautier »

Hi there

Sorry we re new to UaExpert, so apologies if it s a dumb question! we are facing an issue with the data logger. When we try to add a node that describes a date / time or a string with the job reference, then we get an error "Datalogger error : only numeric variables can be added to datalogger view, discarding node xyz" is this expected behaviour ? How can we log to a file non numerical data then? (it works like a charm for numerical data)

Thanks a lot for your help

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Support Team
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Re: Datalogger error : only numeric variables can be added?

Post by Support Team »


the DataLoggerView (like all other plugins of UaExpert) is an "example" to demonstrate the principals of functionalities of the OPC UA technology.

The DataLogger is demonstrating the mechanizm of "sampling", and "queue", and "publish" notifications and how those three interact. (BTW in DAView you can also configure and use those three features, but you hardly can "see" the effect.)

DataLogger is writing to text file, which is just a simplified function, limited in speed (by hard disk) and limited in volume (by file size) and limited to numeric values (by intention). However, when looking at the csv file, you can much better see the effect and understand the cool features of OPC UA and their advantages. It is not planned to write extension objects or strings or the like to the simple csv text file.

If you start writing your own data logger application (using one of our OPC UA Client SDK) you would probably do better, write to some high speed database of your choice, being capable of storing objects and structures of any kind and in any size.
Best regards
Unified Automation Support Team

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