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Lt. Commander

[import] Calculated point using SCADAPack points with no unsolicited RTU event deviation

>>Message imported from previous forum - Category:ClearSCADA Software<<
User: rlao, originally posted: 2019-04-29 00:45:42 Id:419
Hi all,

I have a calculated point (Point A) that simply calculates the difference in value between two SCADAPack analog points from different outstations (Point B & Point C). Points B & C have RTU Event Deviation set to Enabled only (i.e. not Enabled Unsolicited). I originally had Point A set to execute on Tag Processed.

Consider an example scenario where the Point B RTU sends its filled event buffer to SCADA. As part of that unsolicited message, it sends around 20+ timestamped values for Point B. Point A sees that Point B has been processed and executes.

The problem is that it queues up 20+ calculation cycles, one calculation for each timestamped value that Point B has received. Furthermore, each of those calculated values of Point A are all timestamped identically with the time of calculation, rather than synced to the timestamp of the Point B value that triggered the calculation.

Because of the above scenario, Point A gets updated with a flood of values with the same timestamp. Out of all those values, only the most recent one has any real use to us and the rest just muddies up the historic trending. Therefore, is there a way to have Point A calculate only once off the most up to date value from Point B's event dump?

Currently, I've changed Point A to calculate periodically which is fine for now, but it would be useful if I can get an event-driven calculation cycle over a periodic one.


Reply User: dmercer, posted: 2019-04-29 04:17:53
It won't completely solve your problem, but setting Timestamp to "Time of Latest Tag" might help.


Reply User: adamwoodland, posted: 2019-04-29 22:50:51
You could look into Historic Calculation objects and see if they do what you want, alternatively you could write some ST that goes back through the historic of both points and does the calcs (although it is not very scalable a solution and you need to be careful with the queries used)