DWDT Get Waveform Subset VI

Retrieves a subset of a waveform at a specified time or index. You must manually select the polymorphic instance you want to use.


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Inputs/Outputs

  • cbool.png open interval? (T) —

    open interval? defines whether the waveform subset extracted is an open or closed interval. The default is TRUE, which selects an open interval.

    For example, if t0 = 0, dt = 1, Y = {0, 1, 2}, start/duration format is Relative Time, start samples/time is 0, and duration is 2, an open interval returns {0, 1}. A closed interval returns {0, 1, 2}.

  • cu16.png start/duration format —

    start/duration format specifies if you want to retrieve the data value of the specified element or at a specified time.

    0Samples (default)—Returns the data value of the specified element in the waveform data.
    1Relative Time—Returns the data value at a specified time relative to the first point in the waveform. In this mode, the dt of the waveform affects actual start samples/time and actual duration.
  • cdigwdt.png waveform in —

    waveform in is the digital waveform for which you want to retrieve a subset.

  • cdbl.png start samples/time —

    start samples/time is the data element or time value where you want to start acquiring a waveform subset.

  • cdbl.png duration —

    duration is the amount of time to retrieve data or the number of elements of data you want to retrieve, depending on the start/duration format you select.

  • cerrcodeclst.png error in (no error) —

    error in describes error conditions that occur before this node runs. This input provides standard error in functionality.

  • idigwdt.png waveform out —

    waveform out is the waveform subset.

  • idbl.png actual start samples/time —

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

  • idbl.png actual duration —

    actual duration is the actual number of elements retrieved or the actual amount of time the data values were acquired.

  • ierrcodeclst.png error out —

    error out contains error information. This output provides standard error out functionality.

    • For example, consider a waveform of 128 scans with a dt of 1.00. If you wire 40.00 to duration and 25.00 to start samples/time, the actual duration and actual start samples/time are the same, 40.00 and 25.00, respectively. However, if the waveform has a dt of 2.00, the actual duration and the actual start samples/time are 40.00 and 24.00, respectively.

    Examples

    Refer to the following example files included with LabVIEW.

    • labview\examples\Waveform\Waveform - Get Subset.vi