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Thread: Fake alarms during short connection failure

  1. #1
    Join Date
    10.05.2021
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    10

    Ausrufezeichen Fake alarms during short connection failure

    Hello,

    I use Allen Bradley DF1 protocol to communicate with MicroLogix PLC. After short interruption of ethernet connection I get a lot of fake alarms repeated constantly. A lot off bool variables change its value from zero to one and vice versa.

    Best regards

  2. #2
    Join Date
    01.07.2008
    Location
    Salzburg, AT
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    983

    Default Re: Fake alarms during short connection failure

    if you do not want to have alarms because of connection loss (while connection loss variable status becomes INVALID and value 0) then link your variables with reaction matrix evaluating as well value as status bit INVALID (either SPONT). You can create own data type including link to the right rema. Or by connection loss deactivate alarming.

  3. #3
    Join Date
    10.05.2021
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    10

    Default Re: Fake alarms during short connection failure

    I think this problem should be solved with driver update, patch, etc. Because lost of connection must not be reason for fake alarms, Zenon somehow changes states of each variable even it is not coming from real industrial process. It is not about one variable indicating communication quality. It is about huge amount of data changing its fake values in the loop. Only application restart helps.

  4. #4
    Join Date
    01.07.2008
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    Salzburg, AT
    Posts
    983

    Default Re: Fake alarms during short connection failure

    zenon does NOT fake some alarms, your design of the project decided to produce alarms by connection loss. Fix your projecting of variable limits.

  5. #5
    Join Date
    10.05.2021
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    10

    Default Re: Fake alarms during short connection failure

    Can I send you project backup as well as video clip about this behaviour please? What is the best way to send these files?

  6. #6
    Join Date
    01.07.2008
    Location
    Salzburg, AT
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    983

    Default Re: Fake alarms during short connection failure

    I do not need your video to know what happens. You’ve created variables basing on the data type BOOL like delivered in zenon by default. Then you configured the variables: by limit for value 1 to be an alarm. So you are using this data type like predefined for the most of our customers, but not like suitable for your particular needs. If you have special expectations, you have to project it.

    The general rule of all zenon drivers is that by connection loss all affected variables get value 0 and status INVALID ("red squares"). The zenon drivers are doing this because during the connection loss nobody knows what are the current values, they are changing in PLC but zenon does not receives those updates. Thus, to keep last received values in zenon and display for users old data would be the fake information. zenon always shows what it has received from PLC or value 0 and INVALID, no fakes that something works while it is not working.

    Later, when driver succeeds to reconnect with PLC, it reads all data and updates variables with value received from PLC and status SPONT (not INVALID anymore). And - exactly this update causes in your project the alarms. Solution (like i've already posted): create a Reaction Matrix (e.g. multi-binary) to evaluate 3 states:
    - any value but status bit INVALID (no alarm),
    - value 0 and status SPONT (no alarm)
    - value 1 and status SPONT - alarm.
    Then link this reaction matrix in your BOOL data type and make sure variables are inheriting this data type update also for limits.

  7. #7
    Join Date
    10.05.2021
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    10

    Default Re: Fake alarms during short connection failure

    Yes, I understand how it works. But this happens if connection failure is shorter then driver timeout. For example if timeout is 3 sec. and connection failure is 5 sec. long no problem then. But if the connection failure takes 2 sec. then described problem occurs. However, if I have values in the PLC with zero value all the time, I should not have value 1 in zenon database in any case.

  8. #8
    Join Date
    01.07.2008
    Location
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    Default Re: Fake alarms during short connection failure

    In this case connect your local COPA-DATA Support officially; a public forum is not the right place to analyze project and logs.

  9. #9
    Join Date
    10.05.2021
    Posts
    10

    Default Re: Fake alarms during short connection failure

    I will contact local support. Thank you for your answer and previous suggestions.

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