ILX Lightwave LDX-3200 Series User Manual page 116

The LDX-3200 Series Current Source implements a two-point calibration for the current source. Two currents
(approximately 20% and 80% of FS) are applied to a test load, and the resulting actual currents are fed back (by the
user) to the Current Source. The Laser Current Source calibration program uses the two sets of data to calculate new
calibration constants. These calibration constants are used to set the actual current of the current source.
The following procedure is for calibrating each range of the current source. Start with the low range. After calibration
is complete in this range, switch to the high range and repeat the procedure.
Configure the Current Source in the following manner for the Laser Current Source calibration:
FUNCTION
LASER MODE
RANGE
LIMIT
SET POINT
a. Measure and record the resistance of a 1 Ω, 20 W resistor (a 4-point probe 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.
--where E is the accurately measured voltage across the resistor, and R is the accurately measured load
resistance. 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-3200 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.
CALIBRATING THE LDX-3200 SERIES CURRENT SOURCE
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STATE
I (constant current low bandwidth)
low (lowest per instrument model)
90% of FS (full scale of range)
80% of FS
I = E / R
PAGE 7
GPIB COMMAND
LAS:MODE:ILBW
LAS:RAN x
LAS:LIM:Ix
LAS:LDI
CHPT 6