Can I sample different channels at different rates in a task?

[jmcglump]

I am using a NI 9203, 9215, and 9211 modules in a single CompactDAQ chassis. Software is LabVIEW 8.6.

My VI uses DAQ Assistant to sample all three modules within a single While Loop. I can run the whole loop up to about 13 kS/S with no problem. However, around 14 kS / s I get the following error:

"Error -200361 occurred at DAQmx Read (Analog 1D Wfm NChan NSamp).vi:3

Possible reason(s):

Measurements: Onboard device memory overflow. Because of system and/or bus-bandwidth limitations, the driver could not read data from the device fast enough to keep up with the device throughput.

Reduce the sample rate, or reduce the number of programs your computer is executing concurrently."

I need to sample the 9215 signals at up to 20 kS/s, but the signals from the 9203 & 9211 need only be sampled at 1 S/s. Could reducing the sampling rate on the 9203 & 9211 signals solve my problem? If so, how do I implement those different sampling rates within the same DAQ Assistant VI?

[KyleBryson · Accepted solution]

Hi jmcglump,

You can only use one analog input task at a time on a cDAQ-9172 chassis, so you'll need to sample all the modules at the same rate.  You won't be able to do multiple rates in the DAQ Assistant, or to use multiple DAQ Assistants to accomplish this.

However, the rates you are listing give a pretty strong clue.  The cDAQ-9172 is capable of much higher bandwidth than you're getting.  It sounds like you're connected to a Full-Speed USB port, instead of a Hi-Speed USB 2.0 port, which will give you up to 40 times the bandwidth.  Can you make sure that you're using a Hi-Speed capable host controller, as well as any hubs you are using?

Please post more about your PC hardware if that doesn't seem to solve it, and post any additional questions.

Regards,
Kyle 

[jmcglump]

Kyle,

Thanks for the feedback. I'm using a USB extender cable to go from the cDAQ-9172 to my PC (they're located in separate rooms). After a close look, it appears that said USB extender cables are not USB 2.0 standard. We are in the process of acquiring cables that are. I shall post back and let you know if that corrects the problem.

Best,

Jonathan

[jmcglump]

The USB 2.0 extender cables solved the problem. Thanks again!

Jonathan

[ashishji255]

Hello

I am facing one problem in signal express but i don't know why it happens ??

i am able to acquire the signal using analog channel zero but problem is that after recording one or two signals then it showing ERROR message like

"

Error -200361 occurred at DAQ Assistant



Possible Reason(s):

Measurements: Onboard device memory overflow. Because of system and/or bus-bandwidth limitations, the driver could not read data from the device fast enough to keep up with the device throughput.

Reduce the sample rate, or reduce the number of programs your computer is executing concurrently.

"

If i go for the reset the channel then that provlem is solved.

so please give me the solution of it

[Dennis_Knutson]

You should either post a new question to the Multi-Function DAQ or SignalExpress boards. If in fact you are truly using SignalExpress. Your topic says LabVIEW and they are not the same thing.

In your new post, attach your code.