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6000 Series Oscilloscope User’s Guide
5
Making Measurements
FFT Measurement
FFT is used to compute the fast Fourier transform using
analog input channels or math functions 1 + 2, 1 – 2, or 1 *
2. FFT takes the digitized time record of the specified source
and transforms it to the frequency domain. When the FFT
function is selected, the FFT spectrum is plotted on the
oscilloscope display as magnitude in dBV versus frequency.
The readout for the horizontal axis changes from time to
frequency (Hertz) and the vertical readout changes from
volts to dB.
Use the FFT function to find crosstalk problems, to find
distortion problems in analog waveforms caused by amplifier
non-linearity, or for adjusting analog filters.
FFT Units
0 dBV is the amplitude of a 1 Vrms sinusoid. When the FFT
source is channel 1 or channel 2 (or channel 3 or 4 on
4-channel models), FFT units will be displayed in dBV when
channel units is set to Volts and channel impedance is set to
1 M
Ω
.
FFT units will be displayed in dBm when channel units is
set to Volts and channel impedance is set to 50
Ω
.
FFT units will be displayed as dB for all other FFT sources
or when a source channel’s units has been set to Amps.
DC Value
The FFT computation produces a DC value that is incorrect.
It does not take the offset at center screen into account. The
DC value is not corrected in order to accurately represent
frequency components near DC.
Aliasing
When using FFTs, it is important to be aware of frequency
aliasing. This requires that the operator have some
knowledge as to what the frequency domain should contain,
and also consider the sampling rate, frequency span, and
Summary of Contents for InfiniiVision DSO6014L
Page 2: ...Agilent Technologies Agilent 6000 Series Oscilloscopes User s Guide...
Page 59: ...58 6000 Series Oscilloscope User s Guide 1 Getting Started...
Page 109: ...108 6000 Series Oscilloscope User s Guide 2 Front Panel Controls...
Page 125: ...124 6000 Series Oscilloscope User s Guide 3 Viewing and Measuring Digital Signals...
Page 251: ...250 6000 Series Oscilloscope User s Guide 5 Making Measurements...
Page 287: ...286 6000 Series Oscilloscope User s Guide 6 Displaying Data Interpreting Decoded LIN Data...
Page 321: ...320 6000 Series Oscilloscope User s Guide 7 Saving and Printing Data...
Page 370: ......
