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What amount of scan overhead is expected for the USB-2408 &...

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What amount of scan overhead is expected for the USB-2408 & USB-2416


The AInScan function can be used with the USB-2408 and USB-2416, to scan one or more channels, at a fixed rate for a desired number of samples.  For non-continuous scans, the duration of the scan is expected to be:  ((total # of samples) / (# of channels) * (rate in Hz)) + some amount of overhead (to set up, and later stop / clean up, the scan).   The overhead should be on the order of 100 mS, but MCC has discovered certain cases where the overhead is between 1 and 2 seconds.    In order to prevent this abnormally high overhead, you choose the total # of samples to be an integer multiple of 16.

MCC expects to reduce this added overhead as much as possible in a newer revision of InstaCal/UL.   As of this writing, version 6.23 and below have this issue.  it is not clear yet if ver 6.24 will be the first version with the remedy.

In any case, the data returned is valid, both in voltage or temperature level, and in sample rate.   The extra overhead is all at the end of the scan, after all data has been collected.



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Article ID: 50348

Last Modified:4/3/2012 1:40:21 PM

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