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How to generate a message every time a tag changes

Created by: nghaiha at: 8/19/2007 9:19 AM (7 Replies)

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8/19/2007 9:19 AM	Rate (0)
nghaiha Posts: 33 Rating: (3)	I want to know the simpless way to monitor a tag, every time this tag changes, a message is generated. Do I have to write a global script to monitor this tag, each time this tag changes, I toggle a bit in another tag to generate message.
nghaiha Posts: 33 Rating: (3)
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8/19/2007 11:07 AM	Rate (0)
Nemo Posts: 3149 Rating: (171)	hi monitoring by global script is quite bad for your performance.... Did you already check the WinCC manuals / Getting started for this issue?? http://support.automation.siemens.com/WW/view/en/17356933 (e.g. chapter 4.5) http://support.automation.siemens.com/WW/view/en/15342782 http://support.automation.siemens.com/WW/view/en/25158897 http://support.automation.siemens.com/WW/view/en/11841512 http://support.automation.siemens.com/WW/view/en/6905621 nemo
Nemo Posts: 3149 Rating: (171)
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8/20/2007 6:04 AM	Rate (0)
nghaiha Posts: 33 Rating: (3)	Nemo hi monitoring by global script is quite bad for your performance.... Did you already check the WinCC manuals / Getting started for this issue?? nemo Hi nemo, Of course, I checked the WinCC manuals already and also some more documents. But the problem is: In "Alarm Logging" I let "MessageTag" is the tag I want to monitor and "MessageBit" is 0, when the tag changes from 0 to 2, to 4, to 6, etc... the MessageBit doesn't change, right? so no message is issued. That why I think we should have another solution.
nghaiha Posts: 33 Rating: (3)
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8/20/2007 8:10 AM	Rate (0)
Nemo Posts: 3149 Rating: (171)	Hi if I got your problem you are intending to use single bits for setting/resetting alarms? http://support.automation.siemens.com/WW/view/en/17778440 In my opinion you should perhaps use Tags as mentioned in the FAQ above for using group displays - a really nice WinCC featue.... nemo
Nemo Posts: 3149 Rating: (171)
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8/21/2007 9:35 AM	Rate (0)
nghaiha Posts: 33 Rating: (3)	Hi nemo, I still cannot solve this problem, a clearly example will help me much. Nemo if I got your problem you are intending to use single bits for setting/resetting alarms? nemo Till now, I don't know any way else for setting alarms. With this method, an alarm message is only issued when a single bit is toggled (from 0 to 1 or 1 to 0). So it doesn't meet my demand that is to issue message every time a tag changes.
nghaiha Posts: 33 Rating: (3)
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8/27/2007 11:49 AM	Rate (0)
nghaiha Posts: 33 Rating: (3)	Plz help me, thanks!
nghaiha Posts: 33 Rating: (3)
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8/27/2007 12:22 PM	Rate (0)
Nemo Posts: 3149 Rating: (171)	Hi if bit-message are not working for you, you can use analog message. You canfind more info about this in WinCC online help > search for "configuring analog messages" ..or you monitor the limits of your tag by activating upper/lower limit in WinCC tag management > your tag > properties > limits/reporting nemo
Nemo Posts: 3149 Rating: (171)
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9/4/2007 9:14 PM	Rate (0)
Danielle Posts: 1275 Rating: (123)	Hi nghaiha, I can't think of any way of achieving what you want other than checking for changes on the PLC side, and then triggering an event bit for Alarm Logging, or creating a WinCC script. For scripts, just keep in mind that if you have too many tags and need to create many sciprts, your system's performance may decrease. Best regards, Danielle
Danielle Posts: 1275 Rating: (123)
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