11.11 The FFT Gadget

Contents

Video Image.png See more related video:Origin VT-0015 FFT

Overview

The FFT Gadget in Origin provides a simple and quick way to examine the frequency spectrum of data plotted in a graph. A region of interest (ROI) control can be used to select a desired range of the data to be analyzed. The FFT spectrum is displayed in a separate preview graph window, and is dynamically updated as the ROI object is moved or resized. The Amplitude axis scale of the FFT result graph can be switched between linear and log scales.

FFT Gadget.png

Origin also provides an FFT tool with an extensive set of options for performing more detailed Fourier analysis.

To Use FFT Gadget

To use this tool, select Gadgets: FFT from the Origin menu when a graph is active.

Description

This function is used to add a rectangle onto a plot to perform FFT. Moving this rectangle, you can observe the FFT effect of the data quickly in the FFTPREVIEW window. All the default settings to perform the FFT are the same as in fft1. Please see this table below.

Window Rectangle
Shift 1
Unwrap phase 1
Factor -1 (Electrical Engineering)
Spectrum Type <auto>
Normalize power to MSA-Mean Square Amplitude

Options on the Preview Graph

There is a floating Options panel, whose default location is near the top right corner of the FFTPREVIEW window. With it, you can customize the preview graph.

Addtool curve fft 3.png
Rescale If you check this box, the graph in the FFTPREVIEW window will rescale automatically when you move the rectangle.
Log Scale If you check this box, the type of the Y-axis will be log 10 base. Uncheck it will turn the type of the Y-axis back to linear.
Keep DC Offset If you want to remove DC offset, clear this check box.

Preferences

Click the triangle buttonAddtool curve fft 4.png on the right side of the ROI object to open the associated context menu. Selecting Preferences from the menu will open the FFT Preferences dialog, allowing you to customize the ROI object.

Show Tool Name (toolname)

Specify whether to show the tool name on the ROI object. The tool name can be specified if this check box is selected.

Fill Color (rectcolor)

Specify the color of the ROI object.

Example

  1. Create a new workbook.
  2. Import the file fftfilter1.DAT which is located in the <Origin Program Folder>\Samples\Signal Processing\subfolder.
  3. Select Plot: Line: Line from the Origin menu to draw a graph.
  4. Make sure the graph is active, then select Gadgets:FFT from the Origin menu. This adds a rectangle onto the plot.
    Addtool curve fft 11.png
  5. Move the rectangle and you can see the corresponding FFT results in the FFTPREVIEW window.
    Addtool curve fft 2.png

Algorithm

Please refer to fft1 algorithm.