01-24-2007 10:00 AM
01-26-2007 05:37 AM
Hi,
Thank you for posting to the NI forums. Are you using DAQmx – if so, what version of DAQmx are you using? I would recommend upgrading to the newest release, Version 8.3.1, if you haven’t already done so.
If that doesn’t help, I think that the first thing to troubleshoot would be the RTSI line. We want to find out whether this problem is due to a bandwidth limitation of the RTSI bus. Try setting up four analog input tasks with the same number of channels per device as your current application. Acquire at the same rate that you are currently using, but do not include any synchronization over the RTSI bus. If you see the same performance decrease, then we’ll know it’s due to a bottleneck in the PC itself. The biggest bottleneck would be from the speed limitations of the data transfer to the hard drive.
Please post back with the results of this test. If you don’t see any improvement, please provide the following information.
I hope these troubleshooting steps help. Please post back with your results. Thanks!
Ed W.
Applications Engineer
National Instruments
01-29-2007 08:19 AM
01-30-2007 09:13 PM
Hi Mike,
Thanks for the update. I’m not sure why you’re not able to achieve these sample rates. I’ll setup a similar system here. If I don’t see the same behavior, then we’ll know it’s something unique to your program; otherwise, there may be a bandwidth limitation on the cards or the PC. I’ll post back ASAP with the results.
Ed W.
Applications Engineer
National Instruments
02-01-2007 09:03 AM
Hi Mike,
I was able to setup a similar system here, but I haven’t been able to reproduce the behavior that you’re seeing. The main difference is that I used LabVIEW instead of Visual C++. Although the CPU usage did rise to 100%, the system performed fine and did not become unresponsive.
If you’d like to keep troubleshooting this issue, please post back with an attachment of your code, and I can try running that here. Thanks!
Ed W.
Applications Engineer
National Instruments
03-28-2007 09:32 AM