Acquiring Waveform Data from an NI DMM in LabVIEW SignalExpress

Publish Date: Oct 06, 2011 | 5 Ratings | 3.00 out of 5 | Print | Submit your review


The NI 407x line of DMMs is capable of performing waveform voltage and current acquisitions. However, there currently is not a step available in LabVIEW SignalExpress that will allow the user to acquire waveform data from a DMM. The attached example is a LabVIEW VI that can be used as a user-defined step in LabVIEW SignalExpress to acquire DMM waveform measurements. Note: you must have LabVIEW Development System installed to use this VI as a step in your LabVIEW SignalExpress project.

1. How the VI Works

The attached LabVIEW code executes the following steps to acquire waveform data from an NI 407x DMM:

  1. Opens a session to the DMM.
  2. Configures the Function (Waveform Voltage or Waveform Current), Range, Rate, and Total Number of Samples.
  3. Initiates the DMM.
  4. If the Total Number of Samples does not evenly divide into the Samples to Fetch at a Time, the example uses the niDMM Read Status VI and the value of its Backlog parameter to retrieve all samples that are available.
  5. Fetches samples until all requested samples are fetched and aborts the acquisition if an error occurs.
  6. Aborts the acquisition.
  7. Closes the session to the DMM.

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2. Using the VI as a User-Defined Step in LabVIEW SignalExpress

Complete the following steps to use this VI as a user-defined step in LabVIEW SignalExpress:

  1. Verify that you have installed LabVIEW Development System 8.5 or later and LabVIEW SignalExpress 2.5 or later.
  2. Extract the attached source distribution to your hard drive.
  3. In your LabVIEW SignalExpress project, click the Add Step button.  Add the step called Run LabVIEW 8.5 VI, found under the Run LabVIEW VI category.
  4. The Step Setup tab for this step will open.  On the Settings tab, click the file folder icon on the Select VI control.  Navigate to the location where you saved the source distribution and select the Fetch & Graph Waveform VI.   Click OK.
  5. You may add inputs by selecting the Connect Input... button.  This will allow you to use the results of previous steps as inputs to configure the DMM waveform acquisition.  Or, you may choose to click the Configure VI tab and configure the acquisition through the VI front panel.
  6. Once you have configured all of the settings, including the Device Name, Function, Range, Sample Rate, Total Number of Samples, and Samples to Fetch at a Time, your project is ready to run.


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