Stanford Research Systems LDC500, Руководство по эксплуатации и обслуживанию

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4.5 Commands 4 – 21
Photodiode Power Setpoint SWPD(?)
{ f }
Set (query) the monitor photodiode optical power setpoint
{
to
f }
, in
mW.
When the laser is operating in CP mode, and
PDMW
YES is set, the
laser current is controlled to maintain a constant optical power, as
measured by the photodiode, at the level set by
SWPD .
Front panel:
LD Settings:
D:-
.
SWPD 23.1
Example:
Multi-step Scan of Laser Setpoint SCAN(?)
{ f, i, g }
Start (query) an output scan of the laser diode output setpoint
{
with
stepsize
f
,
i
steps, and dwell-time
g
, in ms
}
.
In any control mode, the
SCAN
command may be used to initiate
an automated sweep of the laser operating point; this can be useful,
for instance, to obtain L–I curves of a device under characterization.
The first parameter,
f
, is the increment (or decrement, if negative)
in the setpoint variable currently in use. If the instrument is in CC
mode,
f
is a current step in mA; if CP mode, it is raw photodiode
current step (in
μ
A), regardless of the value of
PDMW
. The scan
begins immediately after receipt of the
SCAN
command, starting at
the previous setpoint.
The second parameter,
i
, gives the total number of steps. Note that
if S
+ i · f >
S
max
or S
+ i · f <
0, where S is the starting operating
point, then the
SCAN
command will generate an execution error and
no changes in output will occur.
The third parameter,
g
, is the dwell time for each step in the scan,
in ms. The dwell time must be set larger than the sync delay
h
sync
,
which is set by the
SYND
command. Note that the total time between
setpoint steps is simply
g
.
Following a time
h
sync
ms after each output step, the rear-panel
SYNC OUT BNC has a
∼
10
μ
s long, negative-going TTL pulse. This
pulse can be used to synchronize other test equipment during the
scan.
The query form SCAN? returns a token value of either
OFF 0
, or
ON
1 , based on whether a scan is currently in progress.
SCAN
can only be initiated from the remote interface.
SILD 50 Example:
LDC500 Series Laser Diode Controllers