Racal Instruments 3152A, Руководство пользователя

Страница: 86 / 176

3152A User Manual
Using The Instrument 3-48 Racal Instruments
©
2001
PLL Commands
In PLL mode, the Model 3152A can be used as a slave only.
Use the following commands to program the Model 3152A to
lock to an external reference.
PLL:LOCK ON
This command places the Model 3152A in PLL mode. If no
valid reference signal is applied to the trigger input, the PLL ON
LED remains off. If you feel that the 3152A should lock and it
does not, check the following:
Make sure that trigger level is adjusted correctly
Make sure that the 3152A frequency setting permits lock in the
required range. Two graphs, one for fixed mode and the other
for user mode are given in Appendix A, showing the lock range
relationship between the reference and the internal frequency
settings
PLL:ADJust <value>
applies a phase offset between the reference signal and the
main output. The default value is 0
o
. Phase offsets can be
adjusted between -180
o
and +180
o
. Best resolution for this
parameter is 1
o
, degrading to 36
o
at 10
o
point waveform
samples.
PLL:FINE <value>
applies a fine adjustment to the absolute setting of the PLL:ADJ
command. The default value is 0
o
. Fine phase adjustment is
usable between -36
o
and +36
o
.
As an example of the use of this command, we’ll take a 100
sample waveform. The best phase offset resolution for this
waveform is 3.6
o
(360
o
/ 100 points). If you need to set an
offset of 50
o
, the Model 3152A will accept this value, but will not
be able to set this offset correctly. Since the resolution is 3.6
o
,
the output will offset by 50.4
o
. You can now correct the phase
to exactly 50
o
by using the PLL:FINE -0.4 command.
PLL:LOCK?
queries the PLL’s state. It returns a “0” (OFF) or “1” (ON).
PLL:ADJust?
queries the PLL offset. It returns a value in degrees.
PLL:FINE?
queries the PLL’s fine offset. It returns a value in degrees.