Adjusting The Bias Voltage Of The Monitor Diode; Adjusting The Power Display Of An Internal Monitor Diode - THORLABS ITC502 Operation Manual

2.10 Adjusting the bias voltage of the monitor diode

2.10 Adjusting the bias voltage of the monitor diode
The bias voltage of the internal monitor diode may be adjusted in a range between 0
and 10 V. It is displayed continuously when selecting the display BIAS and can be set
with the potentiometer marked ADJ located next to the LED "BIAS".
The right polarity of the monitor diode can be checked this way:
• Set a correct limit value of the laser current (I
• Set an allowed laser current above the threshold current and switch the
laser on
• Select the display of the monitor current I
the display. If you see a negative sign (-) the polarity is wrong. If you
measure a positive value, the polarity is right and the bias voltage may
be adjusted to the desired value.

2.11 Adjusting the power display of an internal monitor diode

The optical power can be displayed if P
Therefore the monitor current is transferred into a power display that can be
calibrated with the 25-turn potentiometer marked ADJ located next to the LED P
the front of the ITC5xx.
The position of the potentiometer determines the calibration factor.
This is the description of how to calibrate the power display in local mode
using the display of the ITC5xx. 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 the interface.
(Refer to chapter 3, "Remote control by a PC" starting on page 55)
ITC500 / page 38
NOTE
)
LD LIM
and check the polarity of
PD
is selected for display.
LD
NOTE
at
LD