ILX Lightwave LDX-32420 User Manual page 88

The limit clamp function for DC output current applies to the modulated current as
well protecting your laser in any mode. To accomplish setting the current source
limit, use the (PARAMETER) SELECT push button LIM I. Press the
(PARAMETER) SET pushbutton then rotate the adjust knob. Set the limit to 7.5A.
After three seconds, the new parameter value is stored in non-volatile memory.
When the laser current limit is reached, the CURRENT LIMIT error indicator
flashes. The current limit setting is independent of the voltage drop of the device
connected to the laser output, and therefore, no dummy load is required for
precise adjustment of the current limit. Furthermore, since the current limit
circuitry is fully independent of the main current control, the current limit can be
adjusted safely, even while the current source output is active.
Now you are ready to modulate the laser injection current. To enable the Current
Source output, press the push button labeled (MODE) OUTPUT. The
accompanying LED labeled ON will illuminate indicating that the laser current
source's output is enabled. The instrument will drive the current source to the
01_10
FU N C T I O N S A N D FE A T U R E S
Modulating the Laser Current Source
Setting up the Current Source for a modulated laser injection
current is easy. The (MOD) EXTERNAL connector (BNC) on
the front panel is the input for the modulated signal. Connect
a modulating voltage signal from a standard function
generator, for example, to this connector. The modulation
port input impedance is 1 k. The transfer function for the
low and high current ranges of the LDX-32420 are 1A/V and
2 A/V.
Set the LDX-32420 in Constant Current High Bandwidth
Mode by selecting I
HBW
panel. Do this by toggling the (MODE) SELECT push button
until the I indicator is illuminated. Repeatedly pressing
HBW
the (MODE) SELECT switch cycles through the current (I),
optical power (P), or high bandwidth current (I
modes.
Next, set the current source range by selecting the 10A
range indicated by the accompanying LED. You will need to
press the select push button twice to change the range. It
must be pressed twice quickly (within less than one second)
to switch between modes, and the current source output
must be off (MODE ON indicator unlit) in order to change
ranges.
in the MODE section of the front
5
C H A P T E R
) control
HBW
71
LDX-32420
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