help with synchronizing data collection between LabVIEW Modules

[mbrupb]

I have a NI 9227 current model and a NI 9205 voltage module.  I would like to synchonize data collection between the two in order to obtain accurate I-V curves.  Any suggestions on the best way to do this would be appreciated.  Thanks. 

[_enigma_]

This will depend on task timing / chassis configuration.  What is your current chassis setup?

Alexander M

Applications Engineer

National Instruments

[mbrupb]

I am using a cDAQ 9174.  Right now I have the two modules synchronized using the sample clock of the NI 9227.  But I have encountered a problem with this configuration.  Another thread that I started discusses my new problem:

http://forums.ni.com/t5/LabVIEW/Help-with-slowing-the-sample-rate-of-a-DSA-module-below-its/m-p/1795...

Any help you could give me to fix this issue would be immensely helpful.

[_enigma_]

Synchronization should be fairly simple between two modules on the cDAQ 9174.  I would recommend using a single task / sample clock, referencing all input channels from both modules in your virtual channels VI.  Also, be check out a few Multi-Device / Multi-Function systems examples located in the NI Example Finder under the category Hardware Input and Output >> DAQmx >> Synchronization.

Synchronizing DSA, S Series, and X Series Devices With a Single NI-DAQmx Task

On a side note, please refrain from creating multiple threads on the same topic.

Regards,

Alexander M

Applications Engineer

National Instruments

[mbrupb]

I did not post about the same topic twice...the link that I mentioned in my reply is about a different topic.  This thread was generated because I was unable to sync the two  modules at the time at the time it was generated.  I am now able to sync the modules but my data acquisition rate (which is determined by the NI 9227 internal master timebase) is too high for my application.  I need to reduce the data acquisition rate by either averaging samples read by daqmx read or something similar.  Please point me in the right direction towards doing so. 

[_enigma_]

There are a number of ways to average samples in LabVIEW.  I usually recommend using the Mean.vi under the Mathematics >> Probability & Statistics Palette.  Otherwise the good old fashion 'sum all the samples then divide by the number of samples' would work just as well.  I would recommend post-processing or running a simultaneous loop to process the samples to avoid running into timeout errors with your DAQmx task.  Make sure to check out the examples in the NI Example Finder.

Regards

Alexander M

National Instruments