Counter timers 6602 and Wait until

[Tim]

Does anyone have any experience with the Wait Until 32bit usec VI?

I am trying to get this VI to synchronize on a 25000 usec time division.
but it vacillates from 17000 usec to 33000 usec. I am using the Counter/Timer
6602 running on a RT Engine utilizing RT 7.1 code to make my time measurements. When I set the properties of the "Wait Unitll" at a 32 bit ms mode it seems to wait close to 25 ms or 25000us.

What is the deal with the 32 bit usec mode. Has anyone seen problems with this before?
Can I trust what I am recording?

[GValdes]

Hi, Tim,

How are you trying to compare the time between the Wait Until function and the Counter/Timer board? Actually, when you set the Wait Until Next Multiple function to microseconds, it is using the processor clock to wait, compared to a milisecond resolution, which uses the Operating System clock. The processor clock has much less jitter than the OS clock, so I'm surprised to see that you are getting such a huge difference. Could you explain in further detail how are you comparing both clocks?

Thanks,

GValdes

[Tim]

thank you for answering. First I will explain the program setup. I have a Case structure embedded in a While Loop. I am measuring the time it takes for the VI, within the Case structure, to execute. I want this to synchronize to a 24.84 millisecond time stamp. I am measuring the accuracy of the time stamp using a PXI 6602 running on RT 7.1. I have the RT 7.1 Wait Until embedded in the Case Structure. I start the counter just before the Case Structure and Stop it just after the Case Structure. When I use the Non Real Time Wait Until this measure 25 msec on the money, but when I use the RT 7.1 Wait Until it vacillates from 13 msec to 28 msec. Any advice? Also question 1.) Could an embedded wait until cause this, because I don't see this when I run a Wait Until on a stand alone basis? question 2.) Why does it work outside my code and not inside the code? Appreciate your assistance I had no clue it used a different clock.