Math Waveforms 5
Keysight InfiniiVision 3000T X-Series Oscilloscopes User's Guide 111
groups that equals the specified number of detector points. Then, the points
in each bucket are reduced to a single point according to the selected
detection type. The detector types are:
• None — No detector is used.
• Sample — Takes the point nearest to the center of every bucket.
• + Peak — Takes the most positive point in every bucket.
• - Peak — Takes the most negative point in every bucket.
• Average — Takes the average of all points in every bucket.
• Normal — Implements a rosenfell algorithm. This method to picks either
the minimum or maximum sample in every bucket depending on whether
the data is monotonically increasing, decreasing, or varying. For details,
see the Spectrum Analysis Basics application note at www.keysight.com.
When detectors are used, the FFT's output is decimated, and any analysis is
performed on the reduced or detected data set.
• Points per Span — When the FFT (Magnitude) operator is selected and a
detector is used, this softkey specifies the maximum number of points that
detectors should decimate to. This is also the number of buckets that
sampled FFT points are grouped into before the selected detection type
reduction (decimation) is applied.
The minimum number of points is 640.
The maximum number of points, 64K, is the measurement record limit.
• 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.
• Zero Phase Ref — When the FFT (Phase) operator is selected, this softkey sets
the reference point for calculating the FFT Phase function:
• Trigger — the FFT phase is measured from the trigger (time=0) point of the
waveform.
• Entire Display — the FFT phase is measured from the beginning of the
displayed waveform.
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