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POHow to Periodically Updating Labview chart when collecting multi channel data at a high rate
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  1. POHow to Periodically Updating Labview chart when collecting multi channel data at a high rate
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    copied!<p>Looking for some help with a Labview data collection program. If I could collect 2ms of data at 8kHz (gives 16 data points) per channel (I am collecting data on 4 analog channels with an National Instruments data acquisition board). The DAQ-MX collection task gives a 1D array of 4 waveforms.</p> <p>If I don't display the data I can do all my computation time is about 2ms and it is OK if the processing loop lags a little behind the collection loop. Updating the chart in Labview's front panel introduces an unacceptable delay. We don't need to update the display very quickly probably at 5-10Hz would be sufficient. But I don't know how to set this up.</p> <p>My current Labview VI has three parallel loops</p> <ol> <li>A timed-loop for data collection</li> <li>A loop for analysis and processing</li> <li>A low priority loop for caching data to disk as a TDMS file</li> </ol> <p>Data is passed from the collection loop to the other loops using a queue. Labview examples gave me some ideas but I am stuck.</p> <p>Any suggestions, references, ideas would be appreciated.</p> <p>Thanks</p> <p>Azim</p> <p><strong><em>Follow Up Question</em></strong></p> <p>eaolson suggests that I re-sample the data for display purposes. The data coming from the DAQ-MX read is a one dimensional array of waveforms. So I would need to somehow build or concatenate the waveform data for each channel. And then re-sample the data before updating the front panel chart. I suppose the best approach would be to queue the data and in a display loop dequeue the stack build and re-sample the data based on screen resolution and then update the chart. Would there be any other approach. I will look on (NI Labview Forum)[<a href="http://forums.ni.com/ni/board?board.id=170]" rel="nofollow noreferrer">http://forums.ni.com/ni/board?board.id=170]</a> for more information as suggetsted by eaolson.</p> <p><strong><em>Updates</em></strong></p> <ol> <li>changed acceptable update rate for graphs to 5-10Hz (thanks Underflow and eaolson)</li> <li>disk cache loop is a low priority one (thanks eaolson)</li> <li>Thanks for all the responses.</li> </ol>
 

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