Rigol DS1000CA Series User Manual

RIGOL
Copyright ©1998-2008 RIGOL Technologies, Inc.
User’s Guide for DS1000CA Series
2-15
Selecting an FFT Window
DS1000CA series oscilloscope provides four FFT windows. Each window is a trade-off
between frequency resolution and amplitude accuracy. It depends on the desired
measurement and the source signals characteristics to determine the window to use.
Use the following guidelines to select the best window.
Table 2-7 FFT Windows
Window Features Best for measuring
Rectangle
Best frequency resolution
and worst magnitude
resolution.
This is essentially the
same as no window.
Transients or bursts, the signal levels
before and after the event are nearly
equal.
Equal-amplitude sine waves with fixed
frequencies.
Broadband random noise with a
relatively slow varying spectrum.
Hanning
Hamming
Better frequency, poorer
magnitude accuracy than
Rectangular.
Hamming has slightly
better frequency
resolution than Hanning.
Sine, periodic, and narrow-band
random noise.
Transients or bursts where the signal
levels before and after the events are
significantly different.
Blackman
Best magnitude, worst
frequency resolution.
Single frequency waveforms, to Find
higher order harmonics.
Key points:
FFT Resolution: The quotient between sampling rate and number of FFT
points. With a fixed FFT points, the lower sampling rate results in better
resolution.
Nyquist Frequency
The highest frequency that any real-time digitizing oscilloscope can acquire
without aliasing. It’s normally half of the sample rate. This frequency is called
the Nyquist frequency. Frequency above the Nyquist frequency will be under
sampled, causing a situation known as aliasing.

Rigol DS1000CA Series Specifications

General

Brand	Rigol
Model	DS1000CA Series
Category	Test Equipment
Language	English