Dead band for data

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This topic contains 6 replies, has 2 voices, and was last updated by Mikhail Mikhail 3 years, 7 months ago.

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  • #816
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    GerritDogger
    Participant

    Hello,

    I’m exporting data to a SQL Server using the export module. However my floating point values are changing a lot but I want to filter out these changes to only log changes which are more than a certain dead band.
    How can I do this filtering for the data I’m reading using modbus. I do not mind filtering in the modbus driver, the SCADA server or the export module.

    Thanks for your help

    #817
    Mikhail
    Mikhail
    Moderator

    Hello,

    I think you should add a filtering condition in SQL script in the export module or create a stored procedure that contains a filter and execute it in the export module.

    Something like this:

    INSERT INTO CnlData (DateTime, CnlNum, Val, Stat) 
    VALUES (@dateTime, @cnlNum, @val, @stat)
    WHERE @val > 100 -- filtering
    
    #818
    Mikhail
    Mikhail
    Moderator

    If you mean you need export changes when the difference between the current and the previous values is greater than a deadband (curVal – prevVal > deadband), it is better to use a stored procudure because logic is more complex.

    What is the reason for filtering? If you try to minimize communicating with SQL Server my approach is not suitable for the case.

    #819
    Avatar
    GerritDogger
    Participant

    Thanks for the suggestions. I’ll look into it. However it would be nice to be able to have a filtering (deadband) for each point in the input channels configuration so each point can have its own deadband value. Next the communication server uses this dead band value so that only significant value changes are being handled by the system.

    As soon as I have more time I’ll let you know how I could get the system to work as I need.

    #820
    Mikhail
    Mikhail
    Moderator

    I’m looking forward to receiving news from you

    #821
    Avatar
    GerritDogger
    Participant

    Hi Mikhail,

    Finally it will not be a good solution for me to use a stored procedure to compare with the last value and only log when the change is more than a certain value. This is because we want to log a more than 1500 tags (I do not know the exact amount yet) and I would need to have different values for the deadband for different tags. We will use the minute archive data instead.

    I still think that a deadband in the communication server would be a nice feature to reduce the amount of realtime data.

    Thanks for your help

    Best regards,

    #822
    Mikhail
    Mikhail
    Moderator

    Hi Gerrit,

    Thank you for the information.
    I think deadband is useful for exporting to an external DB, because DB may become a bottle neck. Rapid SCADA itself is fast and deadband is not very important.

    I’d like to improve the Export DB module in the future. I’ve written this idea in the internal tracker.

    Also you can variate a delay after polling in SCADA-Communicator to decrease a volume of information.

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