78 Keysight InfiniiVision 2000 X-Series Oscilloscopes User's Guide
4 Math Waveforms
• 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.
• Blackman Harris — window reduces time resolution compared to a
rectangular window, but improves the capacity to detect smaller impulses
due to lower secondary lobes.
• Vertical Units — lets you select Decibels or V RMS as the units for the FFT
vertical scale.
• Auto Setup — sets the frequency Span and Center to values that will cause
the entire available spectrum to be displayed. The maximum available
frequency is half the FFT sample rate, which is a function of the time per
division setting. The FFT resolution is the quotient of the sampling rate and
the number of FFT points (f
S
/N). The current FFT Resolution is displayed
above the softkeys.
3 To make cursor measurements, press the [Cursors] key and set the Source
softkey to Math: f(t).
Use the X1 and X2 cursors to measure frequency values and difference between
two frequency values (ΔX). Use the Y1 and Y2 cursors to measure amplitude in
dB and difference in amplitude (ΔY).
Scale and offset considerations
If you do not manually change the FFT scale or offset settings, when you turn the horizontal
scale 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 horizontal scale knob will not change the
span or center frequency settings, allowing you see better detail around a specific frequency.
Pressing the FFT Auto Setup softkey will automatically rescale the waveform and span and
center will again automatically track the horizontal scale setting.
To Next Page
Loading...
Need help?
General
