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Making Measurements
FFT Measurement
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 from 54620-series) to channel 1. Set sweep speed to 10
ms/div, vertical sensitivity to 1 V/div, Units/div to 10 dB, Offset to -28.0 dB,
Center frequency to 5.00 kHz, frequency Span to 10.0 kHz, and window to
Hanning.
FFT measurements
FFT Measurement Hints
It is easiest to view FFTs with Vectors set to On. The Vector display mode is set in
the Display menu.
The number of points acquired for the FFT record 2048 and when frequency span is
at maximum, all points are displayed. Once the FFT spectrum is displayed, the
frequency span and center frequency controls are used much like the controls of a
spectrum analyzer to examine the frequency of interest in greater detail. Place the
desired part of the waveform at the center of the screen and decrease frequency
span to increase the display resolution. As frequency span is decreased, the number
of points shown is reduced, and the display is magnified.