Index Waveform Bug - can't index by relative Time.

[Brian_K.]

Hi LVB,

Just so we are on the same page I built an example (in LV 8.2).  I look at the t0 of the original waveform and and the t0 of the subset waveform and they look OK to me.  What are you expecting to see for the t0 after we take the subset.   I posted the example and changes to it that I made.

[LVB]

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@Brian K. wrote:

Hi LVB,

Just so we are on the same page I built an example (in LV 8.2).  I look at the t0 of the original waveform and and the t0 of the subset waveform and they look OK to me.  What are you expecting to see for the t0 after we take the subset.   I posted the example and changes to it that I made.

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I am expecting that actual start samples/time would be the same as the t0 of the subset waveform.  From the documentation:

    "actual start samples/time is the actual data element when the subset was acquired"

If I input a start time, then the output should be actual start time.
If I input a start sample #, then the output should be actual sample #.

Why is this output called "actual start samples/time" if it never outputs a time???

Thanks

[LVB]

See attached image

[Brian_K.]

Hi LVB,

I believe that VI is working and here is why.

The "start/duration format" input defines what format the inputs "start samples/time" and "duration".  In particular Samples makes it so you grab the indexes of the waveform and Relative Time gets subsets of the waveform based on relative time.

"Actual start samples/time" specifies the actual relative time or indexes (based on start/duration) that have been taken as a subset of the original waveform.  For instance in our example VI, make :

"start/duration format" = Relative time,

"start samples/time" = .05,

"duration" = 2.10

If you notice the actual start is put to .10 and the actual duration is 2.00.  In otherwords, since the waveform is a digital representation of the sine waveform, actual values show which way the subset is rounding. 

With that being said, since the mode is set to Relative Time, the inputs and output will be set to relative time of the waveform and not absolute time.  I think I would expect what you want if there was an Absolute Time mode.  Did I do a good job explaining, or why do you think that it should function differently?