"Outputs at Start"group
It would be nice if there were an "Output at start" option to output values at the start of an event frame. Currently there is an "Outputs at close" option for Event Frames.
In calculating your UnitStatus, do you use PI Points in your Analysis?
I agree, an "Outputs at Start" option would be very helpful. An example i can think of is if I create an Event Frame Template with an attribute for UnitStatus. In my Analysis I am calculating whether the Unit is Online or Offline. I could add an "Output Expression" at Start so that I can calculate the Unit Status and write that value to the attribute on the Event Frame Template. With this I can include that value form the template on a Notification Rule or an application that we uses to query the Event Frame Templates would have this info on the template and could access it for use in the application.
Brian Deslatte commented
Slight tangent, but when using other trigger methods such as Pulse, would still like to be able to output (on Start and Stop).
One example, if one had a batch counter that needed to be incremented (but needed pulse triggering etc...)
Great idea. Event frames can trigger notifications, typically a notification is exists because there was an issue. In our case, we would like to set "Outputs at Start" so that when the event frame is created there is effectively a "snapshot" of various conditions and configurations that triggered the event. Then the event becomes a better self-contained reference to the issue.
Jim Gavigan commented
In response to Roger Palmen, "Exactly! Or monitor that a batch has bee..."
Yep.... I do this a lot....
Jim Gavigan commented
In response to Roger Palmen, "In a more general sense i typically brea..."
Yes, I will often save the start time of an event as a PI tag and then have a running duration as a PI tag to show the operator....
I use Event Frames to capture OPC AE events. Since i have a start condition that is the most important to capture and now i only can capture at close, it is necessary to have the option to capture "at start" conditions.
In response to Jim Gavigan, "Yes, I will often save the start time of..."
Exactly! Or monitor that a batch has been running longer than expected. Or no batch has been running longer than expected, or...
In response to Roger Palmen, "Yes! So many use cases to think of. In m..."
In a more general sense i typically breakup logic into two parts: first determining if something is happening, when did it start and stop?, and secondly recoding an EventFrame on that.
To determine when something happens i create an analysis and output the results to a PI Point. That allows me to answer questions like: how often did this happen? How long was this the case? What was the last occurrence? Those questions i can't easily answer within PI using EventFrames.
The EventFrame i use to do, well, eventframe stuff, and i trigger this on the first PI Point. Having an option to have outputs at start allows to combine this logic into one unit instead of spread over two.
Take a simple batch as an example, i need both a PI Point (when is a batch running) and an EventFrame (batch reporting, visualization) to answer these questions.
You can do that with currently shipping software. Just configure an attribute with a Formula Data Reference and a %StartTime% or %EndTime% substitution parameter.
This would not work if you wish to write the start and end time to a PI Point.
If I have misinterpreted your needs, please let me know.
I want to write to an output when the Unit comes offline. I also want to write to an output when the Unit comes online. I would like to do that with One event frame generation analysis, instead I have to have two. Offline Status analysis writes to the "lastonlinedate" output at the close of the event frame. The Online Status analysis writes to the "lastofflinedate" output at the close of the event frame.
Can you provide some example use cases?
Yes! So many use cases to think of. In many cases you want to know something when it started, and at what time, not when it stopped.