w I completely agree that Timed Loops lend themselves more to RT, however there must be some benefit to using them even on Windows, otherwise why would they have bothered to include them?
It's a Structure, which LabVIEW puts in the Structure Palette. Functions can (usually) be used in LabVIEW and LabVIEW-RT, even if one might not be appropriate. My guess is that years ago, NI put in here, not "worrying" that someone would use it in an inappropriate spot.
So your solution, do you happen to have an example I could see?
Well, here's a VIG called "Clock". When first called, it sets the current Millisecond count in the Shift Register, and subsequent calls get "Milliseconds since first called". Hence a clock. The values come, I believe, from the CPU clock, so it should be precise, if not completely accurate (I think I have those terms right ...). That is, while any particular Clock reading might be off (a millisecond or two), there should be no "drift".
In terms of the requirements the timing accuracy is of high importance given that the entire test is Time vs Weight so the timing needs to be the best it can within the given restrictions of software timed data acquisition. This includes the chart/graph for monitoring purposes as I need to assure the end user that the rate of change as depicted is accurate (to within a few seconds at least)
It should certainly be accurate to within a few seconds -- probably within a (very) few milliseconds.
If I did need to adjust the timing/plot on the fly, what monitored value would I use to determine the offset?
If you are talking about "saved data" (i.e. data written to a file), the pairing of "Value Read" and "Clock" should suffice and be good to within a few milliseconds of Time. If you are talking about "what a human can see during an experiment", now you are talking seconds, or several orders of magnitude lower that the precision of your data. Just remember that you don't really know the rate your data are arriving (unless you compute it from Clock). Should not be a problem.
Bob Schor