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9. APPENDIX 1
9.1. OPTIMIZATION OF SPECTRAL ANALYSIS RECORDING
Using logarithmic sweep
The primary factors which affect the optimization of spectral analysis
recording are as follows:
Maximum permitted statistical error
Scanning speed
Measuring time
_
Relative resolution required
The statistical error,
e,
of an RMS measurement* is given by:
€
where
B
T
1
=
2
JBT
measurement or signal frequency bandwidth (Hz)
averaging time
(se~)
( 1)
Also, the analyzer should sweep, at most, one bandwidth during one
averaging time. This determines a scanning speed (S). If the effective averag-
ing timeT is fixed on the 2010, then
s~J!
T
(2)
S is the scanning speed in Hz/sec.
If equations ( 1) and ( 2) are combined at the I im it where T
=
B/S, then
s
(3)
*
The statistical error of spectral density measurements is
e
=
Wr·
For derivation of
these formalae, see the B
&
K booklet "Frequency Analysis and Power Spectral
Density measurements".
82
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