Lightwave Communications LDX-3232 - Manual (Page 108)

C A L I B R A T I O N A N D T R O U B L E S H O O T I N G
Local Calibration of the LDX-3232 Current Source
92 LDX-3232
C H A P T E R
6
a. Measure and record the resistance of a 1
Ω, 20 W resistor (A 4-wire [Kelvin]
resistance measurement is recommended.) Connect the load resistor across the
LASER output terminals (Laser Anode and Laser Cathode) on the 9 pin connector of
the rear panel.
b. Connect the calibrated DMM across the load resistor. Configure the multimeter to
measure voltage in volts. You will be calculating the actual Laser current in the
following manner using Ohm's Law.
I = V/ R
--where V is the accurately measured voltage across the resistor, and R is the
accurately measured load resistance in Ohms. I is the actual Laser current in Amps.
Note: Check the current measuring range of your multimeter. You may be able to measure
Laser Output current in mA by connecting the meter directly to the outputs of the Laser
Current Source.
c. Press the (MODE) ON switch to turn the current source output on. The output must
be on in order to enter the LASER I calibration mode.
d. Enter the LASER I calibration mode by pushing the (GPIB) LOCAL and (DISPLAY)
SELECT switches at the same time. The display will blank and the Current Source
will drive the current output to the setpoint and the Display will indicate output current
in mA.
e. Calculate the actual current through the load as described in step b. Press and hold
in the (PARAMETER) SET switch and turn the adjust knob until the display indicates
the calculated actual current.
f. Release the (PARAMETER) SET switch. After the (PARAMETER) SET switch is
released, the Current Source will drive the current output to about 25% of the first
calibration setpoint.
g. Calculate the measured current again through the load resistor.
h. Press and hold in the (PARAMETER) SET switch and turn the adjust knob until the
display indicates the actual current as calculated in step g.
i. Release the (PARAMETER) SET switch to accept the second calibration point. After
the (PARAMETER) SET switch is released, the Current Source will calculate the
calibration constants and store them to nonvolatile memory. In low bandwidth
calibration mode, the LDX-3232 Series Current Source will also perform current limit
calibration, indicated by the CURRENT LIMIT LED flashing.
j. Turn the current source output off. Change the Mode to I
HBW
(high bandwidth
constant current mode). Repeat the calibration procedure as described above.
k. Change the output range to high range and repeat the calibration procedure as
described above.
I
PD
Current Calibration
The following procedure is for calibrating the LASER I
PD
(PD monitor) setpoint
and measurement. This procedure calibrates the feedback circuits for constant
I
PD
and constant P
PD
modes. When these values are reached and are stable, the
user enters the actual value of the monitor current, measured with a DMM. The