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Digital Trends and Trend Storage on Data Change

Chris

Hello,

We trend a lot of Digital tags, set to 2-byte storage method, but it would be so much better to storage them at a single bit. Also, we use the Wonderware Historian with the connector utility, all of our tags are configured as Analog with the 8-byte Trends stored as doubles and the 2-byte Trends stored as Integers. We have to set the engineering units to T/F and the range 0,1 to help sort them.

We run very fast trending, 100-250ms and it uses a lot of storage, we typically save about 13 months of data per site and I thought it might be possible to use the trigger in the Trend tag configuration to only store when the Variable tag data has changed. Has anybody done this? If so, what was your methods, workarounds and pitfall?

Thanks,

Chris

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  • Hi ,
    The Citect SCADA Connector V3.0 only supports the publishing of String and Digital Variable Tags. That is, variable tags of data type String and Digital, which have the Historize flag set to TRUE.
    The only way to publish analog values (e.g. INT, LONG, REAL, etc.) is to create a Trend Tag for these variable tags. Then set the Historize flag to TRUE for the Trend tags you want to publish.
    The Trend Tags is a better approach, since the Trend System acts as a value buffer, so even if the Connector is shutdown or disconnected, it can recover from the last known sample value. The same isn't true for Variable tags, since you can only query the current value.
    Hope this information helps.
    Kind regards
    Olivier
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  • Hi ,
    The Citect SCADA Connector V3.0 only supports the publishing of String and Digital Variable Tags. That is, variable tags of data type String and Digital, which have the Historize flag set to TRUE.
    The only way to publish analog values (e.g. INT, LONG, REAL, etc.) is to create a Trend Tag for these variable tags. Then set the Historize flag to TRUE for the Trend tags you want to publish.
    The Trend Tags is a better approach, since the Trend System acts as a value buffer, so even if the Connector is shutdown or disconnected, it can recover from the last known sample value. The same isn't true for Variable tags, since you can only query the current value.
    Hope this information helps.
    Kind regards
    Olivier
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