112 Keysight InfiniiVision 3000T X-Series Oscilloscopes User's Guide
5 Math Waveforms
 
4 To make cursor measurements, press the [Cursors] key and set the Source 
softkey to Math N.
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).
5 To make other measurements, press the [Meas] key and set the Source softkey to 
Math N.
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 following FFT (Magnitude) spectrum was obtained by connecting a 2.5 V, 
100 kHz square wave to channel 1. Set the horizontal scale to 50 µs/div, vertical 
sensitivity to 1 V/div, Units/div to 20 dBV, Offset to -40.0 dBV, Center frequency to 
500 kHz, frequency Span to 1 MHz, 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 
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.