Agilent Technologies InfiniiVision DSO6014L, User Manual

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220 6000 Series Oscilloscope User’s Guide
5 Making Measurements
• Scale
— lets you set your own vertical scale factors for
FFT expressed in dB/div (decibels/division). Press the
Scale
softkey, then turn the Entry knob to rescale your
math function.
•
Offset
— lets you set your own offset for the FFT. The
offset value is in dB and is represented by the center
horizontal grid line of the display. Press the
Offset
softkey, then turn the Entry knob to change the offset
of your math function.
3 To make cursors measurements, press the Cursors key and
set the Source softkey to Math .
Use the X1 and X2 cursors to measure frequency values
and difference between two frequency values (
∆
X). Use
the Y1 and Y2 cursors to measure amplitude in dB and
difference in amplitude (
∆
Y).
4
To make other measurements, press the
Quick Meas
key
and set the
Source
softkey to
Math
.
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
measurement.
The following FFT spectrum was obtained by connecting the
front panel Probe Comp signal (~1.2 kHz) to channel 1. Set
sweep speed to 5 ms/div, vertical sensitivity to 500 mV/div,
Units/div to 10 dBV, Offset to -34.0 dBV, Center frequency to
5.00 kHz, frequency Span to 10.0 kHz, and window to
Hanning.
Scale and offset considerations
If you do not manually change the FFT scale or offset settings, when you turn the
horizontal sweep speed knob, the span and center frequency settings will
automatically change to allow optimum viewing of the full spectrum. If you do
manually set scale or offset, turning the sweep speed knob will not change the
span or center frequency settings, allowing you see better detail around a specific
frequency. Pressing the FFT Preset softkey will automatically rescale the
waveform and span and center will again automatically track the horizontal
sweep speed setting.