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Start time and end time of waveform rising edge

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Dear all,

Could you help to advise why the calculation of the result is different in the attachment.

because I need to find out the start time and end time of the rising edge.

The index find out by Basic Level Trigger Detection VI seems correct, but the time of start and end seems the same.

 

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The reason that the Measurement Info "start time" and "end time" appear to be the same is --- because they are the same.  I'm uncertain what NI was thinking when they added this feature, but it appears to be geared to providing an indication on the Graph or Chart of the position of the Start and End time, measured in LabVIEW's "TimeStamp" units and truncated to "number of seconds since 00:00:00 1 Jan 1904 UTC", ignoring fractional seconds.  Since your rise time is way less than a microsecond, the chances to "catching" a transition around 0.999999 and 1.000000 is very low, so most of the time you'll measure Start Time = End Time (to the nearest second).  Moral of the story -- don't use Measurement Info.

 

Bob Schor

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Thanks Bob Schor, I thought I was missing some configuration. So maybe I should find out the index instead of the time.

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