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Chapter 4
FFT Screen Commands
The SR865A has a basic FFT function accessable from the front panel by selecting the appropriate
[Screen Layout] display (remotely, by setting
of FFT mode can be found in Appendix B .
Note that while FFT configuration commands and queries may be sent at any time, the FFT data query
(
FCRY?
) only returns valid data while the display is showing the FFT.
FFTR(?) { ADC | MIXer | FILTer | i }
The
FFTR i
(i=1) or post time constant filter (i=2).
Example
FFTR FILT
FFTR 2
FFTR?
FFTS(?) { i }
The
FFTS i
The argument i is limited to −20 ≤ i ≤ 20. Vertical scale changes preserve the amplitude
of the top edge of the graph.
Example
FFTS 4
FFTS?
FFTO(?) { x }
The
FFTO x
associated with the top edge of the graph.
Example
FFTO -20.0
FFTO?
DLAY FFT
command sets the source for the FFT to input ADC (i=0), post mixer PSD
Set the FFT source to post time constant filter
Returns the FFT source i
command sets the FFT vertical scale (dB/div) according to the table below.
i
dB/div
-8
2 m
-7
5m
-6
10 m
-5
20 m
-4
50 m
-3
100 m
-2
200 m
-1
500 m
Set the FFT vertical scale to 20 dB/div
Returns the FFT vertical scale i
command sets the FFT vertical offset x (dB). This is the amplitude
Set the FFT vertical offset to −20.0 dB
Returns the FFT vertical offset
or
). A more complete discussion
DLAY BARFFT
i
dB/div
0
1.0
1
2.0
2
5.0
3
10
4
20
5
50
6
100
7
200
SR865A DSP Lock-in Amplifier
Programming
125
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