Academic Company Events Community Support Solutions Products & Services Contact NI MyNI
27 ratings:
 2.77 out of 5     Rate this Document

Using the Waveform Data Type in LabVIEW



Primary Software: LabVIEW Development Systems>>LabVIEW Full Development System
Primary Software Version: 6.0
Primary Software Fixed Version: N/A
Secondary Software: N/A

Problem:
What is the waveform data type and how do I use it? Connecting a waveform to VI terminals of certain data types result in broken wires, but with other VI terminals of the same data type this does not occur, why?

Solution:
The waveform data type is used by LabVIEW and other National Instrument's software such as SignalExpress, TDMS, and the DAQmx API to display and store periodic signal measurements. The waveform data type is a cluster comprised of the following:
 

 

t0

A Time Stamp representing the time at which the signal measurement starts

dt

A double numeric that describes the difference in time in milliseconds between each sample in the signal

Y

A 1D array of doubles that contains the values of the samples of that signal.

Timestamps for each value can be calculated by using t0, dt, and the index for the value. Other arbitrary information can be added to the waveform cluster as variants. This can be useful to attach additional information about the signal to show what manipulation may have already been performed on it.

LabVIEW functions accept the waveform data type. For controls and indicators of some data types, LabVIEW will automatically coerce the waveform allowing you to make the connection, even though the terminal's required data type is not explicitly the waveform type. For example, if you connect a waveform wire to a numeric indicator a red dot will appear on the block diagram icon (to indicate coercion is being applied) and the last value of the Y array contained within that waveform will be displayed on the indicator on the front panel. If the waveform is connected to a 1D array indicator then LabVIEW will simply pass the Y data from the waveform to that indicator.

For the Formula Node or a MathScript Node, LabVIEW will not coerce the data automatically. To be able to present the Y values of the waveform into a Formula node as a 1D array or double numeric’s you will first have to use the Get Waveform Components VI which is found in the Waveform sub palette. Using this function and others contained within the Waveform palette, you can extract or modify data to any part the waveform.

For more detailed information on waveforms see the related links below.


Related Links:
LabVIEW 2013 Help: Waveform VIs and Functions
KnowledgeBase 20A8S9YF: Using Primitive LabVIEW Functions on Waveforms
 


Attachments:





Report Date: 05/18/2007
Last Updated: 08/30/2013
Document ID: 49H3Q5B4

Your Feedback! poor Poor  |  Excellent excellent   Yes No
 Document Quality? 
 Answered Your Question? 
  1 2 3 4 5
Please Contact NI for all product and support inquiries.submit