HP 83480A - Frequency Measurements; Frequency Accuracy

General Purpose Oscilloscope Menus
FFT Menu
Frequency measurements
For best frequency accuracy on peaks
1. In the Channel menu, set the Scaling for almost full scale deection.
2. Set the Span so that the signal of interest is near the horizontal center of the screen (not down at
dc),
but
high
enough
to
avoid
aliasing.
The
left
edge
of
the
screen
is
0
Hz,
or
dc
.
3.
Select
the Hanning
window.
A
higher
number
of
points results
in more
accurate
measurements,
but
also
takes
more
computation
time
.
Depending
on
your application,
you can
balance
between
the
need
for
accurac
y
and
computation
speed
of
the
FFT
.
Frequency
accuracy
The frequency accuracy is the sum of two terms. The rst term is supplied
because there are a limited number of frequency bins, and the measurement
is accurate to plus or minus half a bin. The second term is related to the
accuracy of
the internal oscillator which generates the sample clock.
accur
acy
=
6

f
r
eq
uency r
esol
ution
2
+
0
:
007%
2 sig
nal
f
r
eq
uency

10-31