ILX Lightwave LDX-32420 User Manual page 40

O P E R A T I O N
2
C H A P T E R
Operating a Laser in Constant Power (P) Mode
Next, configure the display by pressing and releasing the (DISPLAY) SELECT
switch until the W annunciator is lit. [LASer:DISplay:MDP]
Adjust the Constant Power setpoint of the LDX-32420 to 10 W. [LASer:MDP 10]
To do this, turn the adjust knob to vary the setpoint. When the adjust knob is
turned, the LDX-3232 automatically changes to setpoint mode as indicated by the
flashing annunciator. Adjust the setpoint to 10 W. After an adjustment has been
made, and the adjust knob is released, the setpoint mode will time out in three
seconds and the display will return to the measurement display mode.
Before the laser output is enabled, the power limit for the laser under test should
be set. In Constant Power mode, this is accomplished by setting a Power limit,
LIM P value [LASer:LIMit:MDP]. The LDX-32420 uses the responsivity value
entered to calculate a power limit as a function of monitor current (I ). This is a
PD
software limit only.
To set the Constant Power limit, use the SELECT push button in the
PARAMETER section to select LIM P. When the LIM P is indicated by the
accompanying LED, the display will indicate the limit setpoint in W. Press the
(PARAMETER) SET push button and then rotate the adjust knob to set the limit to
15 W.
The LIM P is the absolute limit of optical power, as detected by the instrument via
the monitor photodiode feedback loop. In order for this limit to be meaningful, the
monitor photodiode responsivity (CAL PD) must be adjusted correctly. The
LASER output is normally turned off if this limit is reached (See
LASer:ENABle:OUTOFF command in Chapter 4 for instructions on disabling this
function). The maximum LIM P value is 100 W.
Also, in constant power mode the LASER current limit and voltage limit values are
in effect. Be sure they are set correctly corresponding to the laser under test.
Setting of these limits is described previously in "Operating a Laser in Constant
Current (I) Mode".
Now the instrument is configured to operate in Constant Power Mode. In the
MODE section, enable the output of the laser current source by depressing the
OUTPUT push button once [LASer:OUTput ON]. The accompanying LED labeled
ON will illuminate indicating that the laser output is on and current is being driven
to the laser. The LDX-32420 current source will drive the laser to the Constant
Power setpoint and maintain closed loop control.
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01_10 LDX-32420
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