3.1 Presettings
LDC340 / Page 14
3.1.4 Adjusting the power display of an internal monitor diode
The optical power can be displayed if the display P
LD
is selected.
Therefore the monitor current is translated into power display that can be calibrated
with the 25-turn potentiometer marked CAL located next to the LED P
LD
at the front of
the LDC340.
The position of the potentiometer determines which monitor current corresponds to
which optical power.
NOTE
This is the description of how to calibrate the power display in local mode
using the display of the LDC340. When using the IEEE488 interface the
calibration of the optical power is done completely different. The CAL
potentiometer does not affect the value measured via interface.
(Refer to chapter 4, “Communicating with a control computer“ on page 27)
Adjustment
During the whole procedure the laser remains switched off.
First select the operating mode P and the display I
PD
at the LDC340.
Then take the maximum optical output power and the corresponding monitor current
from the datasheet of the laser diode. Sometimes you must calculate one value using
the monitor diode efficiency (parameter
η
).
Now set the pre-set value for the monitor current to this value.
Finally switch to the display P
LD
so that the power belonging to the set monitor diode
is shown. Use the potentiometer CAL next to the LED P
LD
to adjust this display to the
corresponding value of the output power.
