Rev A Nov 2017
Page 24
Chapter 4
Standalone Operation
Photodiode Range
This parameter al lows the correct pho todiode current
amplifier range to be set - see Se ction 3.3.7. Note tha t in
order to be able to do this, the laser must be turned on as
otherwise the photocurrent will be zero. Al so, it makes
sense to carry out this step at the maximum laser po wer
where the photocurrent is also at its maximum. If the laser
diode was turned on at the previous step (during the
maximum laser current adjustment), it will stay on. If it was
not, it can now be turned on by setting the KEYSWITCH to
the ON positio n and pressing the LASER ON button. In
either case, the laser will be ope rated at the maximum
current setting.
Initially always set the PD RANGE switches to the 10 mA
range (all switches must be in the upwards, ON position).
Note that the during the adjustment I
PD
LED is lit to indicate
that photodiode current is being displayed.
Adjust the PD RANGE microswitches on the rear panel until
P
dr
-
is displayed (i.e. the range is OK.)
The switches should always be adj usted from a hig her
range towards the lower ranges, i.e. in the 10 mA -> 1 mA -
> 100 uA -> 10 uA order. If the sequence is not followed, the
display may be incorrect.
P
dr
L
Range too low (under range)
P
dr
-
Range OK
P
dr
H
Range too high (over range)
Press the DISPLAY button to access the Photodiode Gain
Optimization parameter.
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