Using the Scope Functions  3
Agilent U1602B/U1604B User’s and Service Guide  77
FFT (Fast Fourier Transform)
The FFT math function converts a time- domain waveform into 
frequency- domain waveform and the magnitude of the FFT spectrum is 
displayed in dBV. In other words, the readout for the horizontal axis 
changes from time to frequency (Hertz) and the vertical axis changes from 
volts to decibels (dB).
FFT waveforms are useful to determine the harmonic contents and 
distortion in analog waveforms caused by amplifier non- linearity, for 
characterizing noise in DC power supplies or to adjust analog filters.
To perform FFT measurement, follow the instructions below:
1 Press   button to access User menu.
2 Press F3 to access Math function menu.
3 In the Math submenu, press F1 to select the FFT function.
4 After selecting FFT, the submenu of the FFT function is displayed 
concurrently for function properties setting.
Source 
Press F2 to select the source (channel 1 or channel 2) for the FFT. 
V Axis
Press F3 to select vertical scale factor expressed in dB/div. There are four 
scale factors for your selection:
• 1 dB
• 2 dB
The FFT function is only available for model U1604B.