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O P E R A T I O N
2
C H A P T E R
Installation
Laser Diode Connections and Shielding
Before connecting the laser diode to the LDX-3412, be sure that the front panel OUTPUT
switch is in the OFF position (LED unlit). Before turning on the OUTPUT, be sure that the
current LIMIT has been correctly set.
The LDX-3412 output is available through the 9-pin rear panel connector (J105).
The LDX-3412 sources current through pins 8 and 9 to the laser anode (+) and
returns current from cathode (-) through pins 4 and 5.
It is recommended that the connections to the LDX-3412 output be made using
twisted wire pairs with an earth-grounded shield (see Figures 2.4-2.7). The output
conductors are left floating relative to earth ground to suppress AC power-
on/power-off transients that may occur through an earth-ground path. If the output
circuit is earth-grounded at some point (such as through the laser package and
mount), the user must be careful to avoid multiple earth grounds in the circuit.
Multiple earth grounds may provide circuit paths that induce spurious currents in
the photodiode feedback circuit and output leads.
Grounding Considerations
The outputs of the LDX-3412 are isolated from chassis ground allowing either
output terminal to be grounded at the user's option. Figures 2.4 - 2.7 show the
proper earth-ground shielding for the most common laser diode/photodiode
connections.
General Operating Procedure
The LDX-3412 can be operated in several modes. The following operating
procedure is applicable to most common usage.
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LDX-3412
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Plug the LDX-3412 into a properly grounded, three-terminal AC power source which
supplies the correct voltage and frequency for your unit.
Turn on the LDX-3412; allow a one hour warm-up period for rated accuracy operation.
Select the LIMIT DISPLAY MODE and adjust the LIMIT knob to the maximum current that
you wish to source.
Select the desired MODE of operation.
With the OUTPUT off (LED unlit), make the necessary external circuit connections.
Double check to ensure that the correct polarity has been observed when connecting to
laser diodes or other devices which are sensitive to being reversed biased. For proper
photodiode feedback connections, refer to Section 2.5.3.
If the CONST P mode is selected, turn the COARSE and FINE PD GAIN pots fully
counter-clockwise (CCW). This will initially maximize the feedback gain and minimize the
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