User`s guide

Making Measurements 4
5000 Series Oscilloscope User’s Guide 169
.
• Window — selects a window to apply to your FFT input
signal:
• Hanning — window for making accurate frequency
measurements or for resolving two frequencies that are
close together.
• Flat Top — window for making accurate amplitude
measurements of frequency peaks.
• Rectangular — good frequency resolution and amplitude
accuracy, but use only where there will be no leakage
effects. Use on self-windowing waveforms such as
pseudo-random noise, impulses, sine bursts, and decaying
sinusoids.
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.
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.