4 – 18
Remote Operation
4.5.4
Laser limit commands
Laser Diode Voltage Limit
SVLM(?)
{
f
}
Set (query) the laser compliance voltage limit
{
to
f
}
, in V.
The voltage limit is an essential protection feature for the laser diode.
Typically, the user will program
SVLM
to a value slightly greater than
the expected maximum operating voltage, and always less than the
rated maximum voltage, for the laser diode under control.
The current source will
always
turn o
ff
when the measured laser
voltage exceeds the
SVLM
value. If the measured voltage is within
250 mV of the limit, the laser diode
VLim
indicator will flash.
Front panel:
LD Settings:
LD Vlim: 5.25V
.
SVLM 5.25
Example:
Laser Diode Current Limit
SILM(?)
{
f
}
Set (query) the laser diode current limit
{
to
f
}
, in mA.
The current limit has two related, but independent e
ff
ects. Most
importantly, the output current is clamped (by hardware) to never
exceed the
SILM
value under any conditions. The second e
ff
ect
is to limit the current setpoint value,
SILD
. These are not exactly
equivalent, since an additional current o
ff
set can be generated above
SILD
via the analog modulate input.
Note that lowering the
SILM
value below the present value of
SILD
has the side e
ff
ect of “dragging” the
SILD
setting downwards with it.
Also note that if the output range is lowered from 500 mA to 250 mA
(100 mA to 50 mA for LDC500) and the
SILM
value is greater than
250 mA, (100 mA)
SILM
will be lowered to 250 (50).
If the laser current is being actively limited to
SILM
, the laser diode
ILim
indicator will light steadily. The current source can optionally
turn o
ff
when the current limit is reached; this option is configured
by the
AILM
command.
Front panel:
LD Settings:
LD(lim:*
.
SILM 123;SILM?
Example:
123.000
LDC500 Series Laser Diode Controllers
