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AIBurst on LJ12 misses samples

AIBurst Xp LJ12

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3 replies to this topic

#1 zoot661

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Posted 25 March 2015 - 03:02 PM

I am using AiBurst under Windows XP to sample an approximate sinusoidal waveform.

 

The logged data is showing discontinuities suggesting that the sampling freezes for a while

 

The command is

 

    aiStatus = AIBurst( &ljId, 0, NULL, 0, 1, 4, nChannels, nGains, &scanRate, 0, 0, 0, NUMBER_OF_SAMPLES, 2, rawValues, digStates, &overVoltage, 0 );
 
In the attached file, column 1 is a record count, column 2 is the output from an incremental encoder and the other columns are the raw logged values


#2 LabJack Support

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Posted 26 March 2015 - 11:44 AM

Did not get an attachment.  Please try again.

 

Do you see the same issue with LJscope.exe?



#3 zoot661

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Posted 26 March 2015 - 01:16 PM

I have not tried LjScope - I have reattached the file - the png shows an example of the discontinuity

Attached Thumbnails

  • scanLog.png

Attached Files



#4 LabJack Support

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Posted 26 March 2015 - 01:46 PM

Each call to AIBurst gets the specified number of scans at the specified intervals, but there will be gaps between each call to AIBurst. 

 

http://labjack.com/s...users-guide/4.7

 

Since you are doing 2 channels, the max number of scans will be 2048.  In your data the discontinuity shows up every 1024 scans, so I suspect you are passing numScans=1024.

 

For continuous data, you need to use stream mode:

 

http://labjack.com/s...users-guide/4.8

 

http://labjack.com/u12/datarates

 

Note that our newer devices (U3/U6/T7 recommended for new applications at this time) are all much better at streaming.

 

http://labjack.com/products/comparison





Also tagged with one or more of these keywords: AIBurst, Xp, LJ12

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