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UTD1000L User M anua l
Table 6-21
Term Explanatio
n
FFT Resolution:
NYQUIST Frequenc
y
def ined as Quo ti en t b et wee n s a mp l e rat e a nd oper a tion poin ts . W h en opera ti on 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
Hannin
g
Hammin
g
Blackma
n
Rectangle
Feature
s
Comp are d with r e ctangl e type, it has
better amplitude
．
accuracy and less
so for frequency resolutio
n
Freque nc y resol uti o n fo r Hammin g i s
a little bette r tha n t ha t o f Ha nn in
g
．
Offers b est ampl itude a c cu r ac
y
．
an
d
worst for the frequency resolutio
n
Offer best frequency resolu tion, but
worst for the amplitude accuracy. No
big c ha ng e b efo re a nd afte r add i n
g
window function
.
Used to measure sine, periodic and narrowband
random noises
.
Used to measure t ransient or short pulse
after
；
．
and fo
r
signals whose signal levels before and
the event are greatly differen
t
Mainl y for me asur i ng singl e freque ncy signa l s a nd
looking for higher
order harmonics
A
pplicable for measuring transient or short pulse
,
the si gn al l ev els befo re a nd after t he event a r e
app rox im ately equal. And also f or mea su ri ng equa l-
amp litude s in ewave w ith ve ry c l os e freque nc i es
,
broadband random noise with relatively slow
changing spectrum
.
Best Applications
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