Arroyo Instruments LaserSource 4205, Руководство пользователя

Страница: 20 / 28

Page 20 · 4200 Series LaserSource User’s Manual
applications, part number 1221 is a two meter cable with a male DB-9 on one
end and stripped and tinned leads on the other. Both cables common pins 1/2
and 3/4 into 18 gauge wires.
See the manual for your laser (and fixture) for additional safety and operational
information.
Grounding Considerations
A key feature of the
LaserSource is the optical isolation of both the photodiode
and modulation inputs. By isolating there inputs, earth grounding of the
photodiode anode or cathode, or earth grounding the modulation input, cannot
cause a ground loop through the instrument. Likewise, the laser anode and
cathode connections are also isolated from earth ground.
However, if you use the earth ground pin of the Output connector (pin 3), it is
possible to create a ground loop if the instrument’s earth ground is connected to
a fixture or optical table that is also earth grounded. Make sure that from your
laser diode package there is only a single path to earth ground.
Using Limits
The
LaserSource provides several limit features for protection of the laser
diode. These include current, voltage, photodiode current, and photodiode
power limits.
Both the current and voltage limits are implemented in hardware, providing for
fast response to changes in laser diode operation. When a voltage limit is
detected, the output is immediately shutdown. Because of the sensitivity of the
voltage limit, operating near the limit (within one to two hundred millivolts) is not
recommended. In general, you should set the voltage limit to 0.1V to 0.2V higher
than any anticipated operating point.
Unlike the voltage limit, the current limit simply prevents the
LaserSource from
delivering more current than the limit is set to. When the current limit engages,
the output will remain on. Because of the relative inaccuracy of the current limit
set point, the
LaserSource may detect a current limit condition a few milliamps
before the hardware limit actually engages.
The photodiode current and photodiode power limits are implemented in
software and may take up to one second to trigger when these conditions occur,
and therefore should not be relied on to provide fast protection of the laser
diode.