Unable to Wire FFT Power Spectrum and PSD VI to Write to Measurement File Express VI in LabVIEW

Updated Aug 17, 2023

Reported In

Software

  • LabVIEW
  • LabVIEW Signal Processing Toolkit

Issue Details

I am using the FFT Power Spectrum and PSD VI in LabVIEW. Currently, I am able to see the Frequency vs Amplitude Waveform Graph but would like to write that data to a file using the Write to Measurement Express VI . However, I am currently unable to as I only get a broken wire when trying to wire the Power Spectrum output of the FFT Power Spectrum VI to the Signals Input of the Write to Measurement Express VI. What does the data of the Power Spectrum Output contain?



 

Solution

The data coming from the Power Spectrum Output of the FFT Power Spectrum VI contains an array of clusters. You can determine this by the following steps:
  1. Open up Context Help by pressing <Ctrl+H>.
  2. Hover over the wire coming from the Power Spectrum Output
  3. The data that is contained in that wire will be listed (as shown below) in the Context Help window:

Note: The Signal Input of the Write to Measurement Express VI does not take an array or cluster. Therefore, you will have to break down the data further. Ultimately, the data you want to send to the file is dependent on what you need for your application. However, you can get started by using Index Array and Unbundle by Name to see the individual pieces of data. An example of this is shown below. Additionally, instead of using the Express VI, you could use the Write to Text File VI. An example using this VI can be found by navigating to LabVIEW and selecting Help>>Fundamentals>>File Input and Output>>Spreadsheet>>Tab-Delimited Data.lvproj>>Write Tab-Delimited File .vi

 

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