Lightwave Communications LDX-3232 - Manual (Page 112)

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
Remote Calibration of the LDX-3232 Current Source
96 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.
c. The current source output must be on in order to enter the LASER I calibration mode.
Enter the LAS:OUTPUT ON command to turn the current source output on.
d. Enter the LASER I calibration mode by issuing the LAS:CAL:LDI command. The
display will indicate a current in mA.
e. Input the first actual (measured) output current (as an <nrf value>) via the
LAS:LDI <nrf value>
command.
If this value is to be measured and entered remotely via a GPIB controlled DMM, for
example, the measured value of the current should not be entered until the
LDX-3232 Series Current Source is ready to receive it. The Current Source will be
ready to receive the new measured value when, after a LAS:CAL:LDI? query is
sent, the response from the Current Source is "1".
f. Once the newly measured I value is entered via the LAS:LDI command, the Current
Source will apply a new current equal to about 25% of the previous set current.
g. Input the second actual (measured) output current (as an <nrf value>) as in
Step e.
h. Once the second actual I value is entered via the LAS:LDI command, the new
calibration constants will be calculated and stored into non-volatile memory. In low
bandwidth calibration mode, the LDX-3232 Current Source will also perform current
limit calibration as indicated by the CURRENT LIMIT LED flashing. The OPC? query
may be used (after the LAS:LDI value is sent) to determine when the calibration is
completed. Or, wait about two seconds before continuing with other GPIB
commands.
i. Turn the current source output off. Change the Mode to I
HBW
(high bandwidth
constant current mode) with the LAS:IHBW command. Repeat the calibration
procedure as described above.
I
PD
Current Calibration
The following procedure is for calibration the LASER I
PD
constant current source.
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 current, as measured by an external DMM. The LDX-3232 Current
Source then automatically calibrates the LASER feedback circuits.