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Sampling >30 sec at 20kHz into a CONTINUOUS record, i.e. no "gaps"

Hi, everyone
I'm using labview 8 and I want to sample a large amount of data and write it to a file. The sampling frequency lies around 20 kHz with up to 20 channels and more than 30 seconds of time. This constitutes a large amount of data, and reading it in "one chunk" is not possible. This ought to be one of the most usual tasks in labview, but i can't find a single template, example or chapter in the manual that shows me how to do this WITHOUT GETTING GAPS IN THE TIME-RECORD. If I put the DAQ Assistant into a for-loop there will be a small delay between each iteration and thus a gap in the record, won't there....?
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Message 1 of 5

What hardware ar u using

If its a multifunction DAQ card, Go to find examples>>Hardware i/o>> DAQmx>> Analog measurements>> voltage>> and open any continous acq example

this should work better for your application

hope this helps



Message Edited by devchander on 03-12-2006 10:24 PM

Message 2 of 5

Thank you, Devchander!

I'm sure this is basic stuff to most of you, but I'm fairly new to LW. Let me get this straight: ANY sampling task using "continuous" will result in a record that has no gaps regardless of the "number of samples" setting once you put it in a loop?



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Message 3 of 5

Yes, That's how data acquired in continous sample mode will appear.

Just choose appropriate number of samples to read for the selected sampling rate.

Also, read the Help for DAQmx read.
Fo the concerned control, it says " If you leave this input unwired or set it to -1, NI-DAQmx determines how many samples to read based on if the task acquires samples continuously or acquires a finite number of samples"
Hope this helps
Message 4 of 5

Hello Einar!

Welcome to National Instruments discussion forums as well as to the LabVIEW world. I hope you will be successful with LabVIEW and that it will allow you to decrease the development cost.

Some good links that describes DAQmx concepts and data acquisition programming in general can be found here:

Complete Data Acquisition Tutorial

Learn How to Install and Use a Data Acquisition Device

Learn 10 Functions in NI-DAQmx and Solve 80% of Data Acquisition Applications

NI-DAQmx Professional Tools

NI-DAQmx Software

Hope this helps and good luck!


Jimmie A.

Applications Engineer, National Instruments


Jimmie Adolph
Systems Engineering Manager, National Instruments Northern European Region

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