NI-6023 digital inputs miss line state-changes

[Rchrd]

I am using the NI-6023 DAQ to monitor digital lines. Occasionally (less than 1% of the time) the 6023 misses a low-to-high line state-change from . LabVIEW 6.1 polls the 6023 every 5 mS. The digital lines are normally low. When they go high, they remain high for only 50 mS.

LabVIEW 6.1
Windows 2000 Professional

[rpursley8]

Are you sure it really is polling every 5 ms? Have you used the timer functions to verify the timing?

[LYu]

Hi Rchrd,

If you're using a loop to poll your digital line, it's possible that you're not actually polling every 5 ms, since this is software timed. The speed is software/computer dependent, hence can depend on factors such as processor activity. Software timed I/O is normally used for low-speed applicatiosn that do not need hardware timed precision. You can do some troubleshooting by checking to see if there's a certain condition under which the state change is missed, and making sure you don't have other applications runing.

Hope this helps.

Thanks,
Lesley Y.