How to save from 8 AI channels to seperate files

[PKP]

Thanks again.

One problem that I am facing with having DAQmx Create Channels in series is that my DAQ has two PXI-6133 boards with 8 channels each. So I have to choose 8 channels on one board, 4 on the other. And this causes the VI to output an error saying "One task cannot have multiple Independant Devices."

So perhaps I should create two instances of the above example, one for each PXI-6133 board.

Philip

[Dynamik]

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Note that while your Channel-scan rate is 100KHz, there's (probably) one, shared, AtoD conveter on the DAQ board, in which case the first sample from channel 0 and the first sample from channel 1 are actually acquired at [slightly] different times.

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More correctly, while your Sampling rate is 100KHz, there's probably a Channel-scan rate - maybe 20MHz - in which case the first sample from channel 0 and the first sample from channel 9 (assuming 0-9 are acquired in that order) would be acquired about 500ns apart - so not precisely "simultaneously".

[Mcdan]

PKP,

Multi-device tasks are not currently allowed in DAQmx (except for 446x and 447x devices).  As a result, you will need to create a task for each of your 6133 devices.  You can share start triggers and sample clocks to ensure that these tasks are synchronized and that you can acquire data across both devices simultaneously.  For an example of this, I would recommend that you look at Multi-Device Sync-Shared Ext Sample Clk.vi in the DAQmx examples.  Although the 'master' device in this example is setup to use an external clock, it should work the same for an internal clock (ie... unwire Sample Clock Source Control).  This will ensure that both devices start and acquire samples simultaneously.

Dynamik,

While your point about the sequential scans of channels is very much a consideration for E-Series or M-Series devices,  S-Series devices such as the 6133 have independent ADC's per channel, and can be clocked simultaneously.

Hope this helps,
Dan

Message Edited by Mcdan on 09-12-2005 06:36 PM

[Dynamik]

Thank you Mcdan,

Thought I'd sufficiently covered my rear with "there's (probably) one, shared, AtoD"!

As it happens, my first LabVIEW program used a four-channel NI board with four AtoDs (one per channel.)  I can't find the board in legacy devices - maybe I'm remembering the name wrong - ever heard of an NB2000?  (the NB stoof for "New Bus".)

Cheers!

[Mcdan]

Dynamik,

I believe that you are sufficiently covered.  I wanted to point out that in this particular instance channel to channel delay was not going to be an issue.  Definitely a valid point to mention for many applications with one of the other families of devices.

I have heard of the some of the NuBus devices (NuBus being a bus for some older Macintosh computers), however these predate my time here.  Out of curiosity I did a little browsing through our website, and there was indeed a device called the NB-A2000.  It appears that it was last supported in DAQ 4.9.4 for Macintosh.

Have a great day!

Dan

[Dynamik]

Thank you Dan,

      I've gotta try to read these posts more carefully...

cheers!

re: NB-A2000, thanks I needed a memory-refresh - Indeed, the app. ran on a 50Mhz (accellerated) MAC.