HOW I FOUND THE LAST TIME CHANGE OF ONE DIGITAL POINT?
Could you please specify your question better? Are you looking at getting the snapshot value of a digital state? For which product do you need this? Processbook, DataLink, maybe PISDK?
The vCampus community is here to help you find your answers, but you really need to specify your question better. This is very important if you want to have the correct answer to your questions.
Please also refrain from using all capital letters, this is percieved as shouting.
I have a tag, which is a digital point, which tells me that the machine is turned on or off using the product ProcessBook, however I would like to get the time of last change, the point on to off or off to on, and thus view this time in ProcessBook screen in a field Value. (no graphics, only the time).
I think you can use the Performance Equation PrevEvent(tag, time) function. This function is meant to find the time of the point's previous archive event relative to the time parameter. Something like PrevEvent('cdt158', '*') should give you the time of the current snapshot value of the tag cdt158, and PrevEvent('cdt158', PrevEvent('cdt158', '*')) would give you the time of the archive value before the snapshot value.
Note: I am assuming that only changes in state are archived, meaning the value "on" will not be stored in archive consecutively. Else the above method may not work.
Creating a calculation dataset with the equation in ProcessBook should give you what you want. But you should take note of the calculation interval setting which determines when the calculation is executed.
Thank you very much
I'm sorry by for the lack of objectivity and context. I will be more clear in next the questions.
Retrieving data ...