I N S T A L L A T I O N A N D O P E R A T I O N
General Operating Procedures
22
LDX-3500 Series
C H A P T E R
2
Power Mode Operation
You can operate the LASER current source portion of the LDX-3500 Series
Precision Current Source in several modes, constant I CW, constant I HBW, or
constant POWER. This example is for constant POWER mode. Refer to Section
2.6.3 for constant I CW or I HBW mode operation.
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Plug the LDX-3500 Series Precision Current Source into a properly grounded, three-terminal
AC power source supplying the correct voltage and frequency for your unit (refer to the back
panel for the correct ratings).
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Turn on the LDX-3500 Series Precision Current Source. The OUTPUT stage will be off at
power-up and the unit will automatically configure its parameters to the state which existed
when the power was last shut off.
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Press the ENBL switch in the ADJUST section of the front panel so that the ENBL indicator is
lit (adjustment enabled). Press the MODE switch until the POWER mode is selected. Press
the RANGE switch until the desired current range is selected.
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Press the PARAMETER switch and check the setting of I LIMIT to insure that it is compatible
with the laser you are using. If not, turn the adjust knob until the current limit is correct.
Press the PARAMETER switch again and check the setting of P LIMIT to ensure that it is as
desired. If not, turn the adjust knob until the power limit is correct.
Press the PARAMETER switch again and check the setting of CAL PD to ensure that it is as
desired. If not, turn the adjust knob until the CAL PD value matches the responsivity of your
monitor photodiode.
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Press the DISPLAY switch and check the set point (operating) power. If it requires changing,
turn the adjust knob until the desired value is displayed.
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Turn the current output on by pressing the ON switch (in the OUTPUT section). The unit will
automatically drive the laser to the set point power. If the laser power exceeds the P LIMIT
setting, the P LIMIT indicator will blink.
If necessary, adjust the PHOTODIODE BIAS on the back panel, as needed.
In POWER mode the output may also be modulated via the MODULATION input. When
modulating in POWER mode the user should take special care to set I LIMIT properly. Since
the monitor diode current (feedback) controls the drive current in this mode, the modulation
bandwidth is limited and the response time of the control feedback (monitor current) greatly
affects the drive current operation.
During operation, the adjust knob may be disabled by pressing the ADJUST ENBL switch.
The LED indicator will be unlit when the adjust knob is disabled.
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When the unit is powered off, the state of the unit at power-down is saved in non-volatile
memory.
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