User Manual

95
UTD1000L
User Manual
Table 6-21
T
erm Explanation
FFT Resolution:
NYQUIST Frequency
defined as Quotient between sample rate and operation points. When operation points are
fixed, the lower sample rate is, the better FFT resolution will be
For waveforms with highest frequency f, it at least needs to apply 2f sample rate in order
to recreate original waveform It is called NYQUIST principle f is NYQUIST frequency and 2f is NYQUIST
sample rate
．
：
． ，
．
FFT Window
Hanning
Hamming
Blackman
Rectangle
Features
Compared with rectangle type, it has
better amplitude
．
accuracy and less
so for frequency resolution
Frequency resolution for Hamming is
a little better than that of Hanning
．
Offers best amplitude accuracy
．
and
worst for the frequency resolution
Offer best frequency resolution, but
worst for the amplitude accuracy. No
big change before and after adding
window function.
Used to measure sine, periodic and narrowband
random noises.
Used to measure transient or short pulse
after
；
．
and for
signals whose signal levels before and
the event are greatly different
Mainly for measuring single frequency signals and
looking for higher
order harmonics
Applicable for measuring transient or short pulse,
the signal levels before and after the event are
approximately equal. And also for measuring equal-
amplitude sinewave with very close frequencies,
broadband random noise with relatively slow
changing spectrum.
Best Applications