Keysight InfiniiVision HD3 Series - Page 66

66 Keysight InfiniiVision HD3-Series Oscilloscopes User's Guide
4 FFT Spectral Analysis
You can use the X1 and X2 markers to measure frequency values and difference
between two frequency values (
∆X). Use the Y1 and Y2 markers to measure
amplitude in dB and difference in amplitude (∆Y).
You can make peak-to-peak, maximum, minimum, and average dB measurements
on the FFT waveform. You can also find the frequency value at the first occurrence
of the waveform maximum by using the X at Max Y measurement.
The FFT dialog box has these controls:
• On — Turns the FFT waveform on or off.
• Y Scale — Adjusts the FFT waveform's vertical scale (units/division), making the
waveform shorter or taller on the display. The vertical scale is displayed in the
FFT badge at the top of the display.
You can also make this adjustment using a touchscreen vertical pinch gesture
in waveform drag mode.
The default mode for expanding the signal when you adjust the vertical scale is
vertical expansion about the ground level of the waveform; however, you can
change this to expand about the center of the display. See
"Setting
Oscilloscope Preferences"
on page 278.
When Fine is not selected (that is, coarse adjustment), the shorter and taller
buttons in the dialog box change the vertical scale in a 1-2-5 step sequence.
When Fine adjustment is selected, you can change the math function's vertical
sensitivity in smaller increments.
• Y Offset — Adjusts the waveform's vertical offset, moving it up or down on the
display. The vertical offset is displayed in the FFT badge at the top of the
display.