04-09-2007 05:56 PM
04-10-2007 10:19 PM
Seaman,
The 9237 is a bridge module, so you can't actually use it in an analog input
task. The 9237 needs to be used for either a strain gauge or a custom
voltage with excitation task. Since the cDAQ chassis only allows one
analog input task at a time, you won't be able to acquire from the 9237 at the
same time as the 9205 or 9211. As the manual explains, "The
cDAQ-9172 has one AI timing engine, which means that only one analog input task
may be running at a time on a chassis." The 9237 must be in a separate
task from the 9205 and 9211.
Sorry for any inconvenience.
04-11-2007 09:50 AM
Hi Seaman-
The source of this limitation is not that you are restricted to a single measurement type in a task, but rather that the timing architecture of the 9237 is different than the other modules you're using. The 9237 is a sigma-delta module that requires the use of a sample clock that is internally-derived from an oversample clock timebase. The other modules simply use a sample clock that is externally-provided or derived from an internal sample clock timebase. These differences make it very difficult to synchronize the two modules using an external sample clock alone.
A better option for strain measurement synchronization with MIO modules via an external clock would be the NI 9219. You should be able to add a simulated 9219 to your task and acquire from all channels with the PFI0 sample clock source on the NI 9205.
Hopefully this helps-
04-11-2007 11:46 AM - edited 04-11-2007 11:46 AM
Message Edited by Elijah K on 04-11-2007 11:47 AM
04-11-2007 02:11 PM
10-07-2011 01:34 PM
Hello
I found this article in NI website and example LabVIEW VI describing how to sync AI DAQ in two cDAQ-9172 chassis.
http://zone.ni.com/devzone/cda/tut/p/id/5376. This example shows how to sync AI DAQ when you have a 9211 or 9215 cDAQ modules. (I found that it did in fact work with 9211 modules). However I wanted to try it with 9234 modules.
Here is my setup:
Chassis #1 - cDAQ 9172
Module 1 - cDAQ 9234
Module 5 - cDAQ 9401
Chassis #2 - cDAQ 9172
Module 1 - cDAQ 9234
Module 5 - cDAQ 9401
The two cDAQ 9401 modules are connected with a DB25-25 cable.
But when I tried this example I too get the error "Error -200414 occurred at DAQmx Start Task.vi:1"
Possible reason(s):
Requested sample clock source is invalid.
Property: SampClk.Src
Corresponding Value: /cDAQ9Mod5/PFI0
Device: cDAQ9
Task Name: _unnamedTask<AC>
So it sounds like the same error that the previous user got with his 9237 modules.
Can you please comment on this and let me know what the problem might be.
Thank you
Sundaram Raghuraman
10-07-2011 03:54 PM
It is not currently possible to synchronize tasks across chassis that use AI modules with delta-sigma ADCs, such as the 9234 and 9237. The DAQmx help has a full list of these modules in the C Series Device Groupings section.
The delta-sigma modules synchronize by sharing a sample clock timebase (and sync pulse), not a sample clock. There is currently no way to share that signal between cDAQ chassis.
10-21-2013 07:24 AM
Hi Tom,
How can I synchornize the module two 9237 and one 9205 with the 9178 chassis ?
Can't I use the external clock, and how?
Hope for your reply.
10-21-2013 12:29 PM
Hi dfffs-
If I read correctly, you just want to synchronize multiple modules in the same chassis. Do you want to use an external clock, or are you asking if you must use one?
If using an external clock is not a requirement, you can synchronize the modules using the internal clock by just including channels from the multiple modules in a single DAQmx task. You can do this by calling the DAQmx Create Virtual Channel VI of your measurement type multiple times, or you can combine channels from multiple modules using comma-separated lists (like 'cDAQ1Mod1/ai0:7, cDAQ1Mod2/ai0:7').
If you have a more involved question than this, please post a new discussion forum thread.
Hopefully this helps-
11-04-2013 07:40 AM
Hi, Tom
Thank you very much. I think I know how to synchronize multiple moduels without external clock now.