22
Chapter 3. Operation
3.2
Achieving an initial lock
The
SPAN
and
OFFSET
controls of the
FSC
can be used to tune the
laser to sweep across the desired lock point (e.g. cavity resonance)
and zoom in on it. The following steps are illustrative of the process
required to achieve a stable lock. Values listed are indicative, and
will need to be adjusted for specific applications. Further advice on
optimising the lock is provided in
§
3.3.
•
Connect the error signal to the “
A IN
” input on the back-panel.
•
Ensure that the error signal is of order 10 mVpp.
•
Set
INPUT
to “∆” (offset mode) and
CHB
to “0”.
•
Set
MONITOR 1
to “
FAST ERR
” and observe on an oscilloscope.
Adjust the
ERR OFFSET
knob until the
DC
level shown is zero
•
Reduce the
FAST GAIN
to zero.
•
Set
FAST
to
SCAN+P
, set
SLOW
to
SCAN
, and locate the reso-
nance using the sweep controls.
•
Increase
FAST GAIN
until the error signal is seen to “stretch
out” as shown in figure 3.2. If this is not observed, invert the
FAST SIGN
switch and try again.
•
Set
FAST DIFF
to “
OFF
” and
GAIN LIMIT
to 30. Reduce
FAST INT
to
∼
100 kHz.
•
Set
FAST
mode to “
LOCK
” and the controller will lock to the
zero-crossing of the error signal. It may be necessary to make
small adjustments to
FREQ OFFSET
and
ERR OFFSET
.
•
Optimise the lock by adjusting the
FAST GAIN
and
FAST INT
while observing the error signal. It may be necessary to relock
the servo after adjusting the integrator.
3
If there is no need to adjust the DC level, the COUPLING can be set to DC and
the ERROR OFFSET knob will have no effect, preventing accidental adjustment.
Содержание FSC100
Страница 1: ...Fast servo controller FSC100 Version 0 1 2 Rev 2 4 hardware ...
Страница 4: ...ii Contents ...
Страница 14: ...10 Chapter 1 Introduction ...
Страница 22: ...18 Chapter 2 Connections and controls ...
Страница 36: ...32 Appendix B 115 230 V conversion ...
Страница 39: ......
