General description
The FFT analyzer displays the signal power spectral density function. The x- axis is the frequency in kHz. The y –axis is the signal power in decibel scale. The power is scaled so that the maximum possible input power of the selected input device corresponds to zero level.
There are two sliders on the right side of the FFT window. The left slider is used to set the middle position of the window. The right slider is used to set the dynamic range. The left mouse button is used for zooming. When the left mouse button is pressed, the selected frequency is shown on the bottom of the FFT window.
Display Settings
The popup menu is activated when the right mouse button is pressed on the top of the view area. The popup menu contains the following menu items:
Stop / Start
The display can be started or stopped using this menu item.
Auto Scale
The window area is scaled automatically according to the signal
Zoom Out
The display area is scaled back to the original size. Use this selection when you want to scale ‘backwards’
Grid
Selected grid lines are drawn.
LogX
The selected x –axis is drawn in logarithmic scale. It is a useful display mode for example for speech signal. Zooming is not supported in this display mode.
Average
If selected, the power spectrum function is averaged on time. Using this display mode, it is easier to see which frequencies contain energy, but fast changes are not shown.
Maximum
If selected, the maximum values are maintained.
Update Interval
Opens an update interval dialog, which is used to set the signal view update rate.
Properties
Opens the power spectrum properties dialog. The resolution of the power spectrum display can be selected between 512, 1024 and 2048 samples. The bigger the value the better is the resolution in the frequency domain. The resolution depends on the sampling frequency too. The average IIR factor parameter is used as IIR gain factor in the averaging process. It is used only when the averaging is on. The smaller gain factor means that new values have less gain compared to the old values.
Copy to Clipboard
Copies the window to the clipboard.
Help
Gives information about FFT analyzer.