ILX Lightwave LDC-3700C Series, Руководство пользователя, Страница: 167 / 176

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
Calibration Overview
04_09 LDC-3700C Series
151
C H A P T E R
5

Current Source Calibration
There are three calibration adjustments required for the LASER current source of
the LDC-3700C Series Laser Diode Controller. They are calibration of the
constant current source for both bandwidths and ranges, calibration of the laser
voltage measurement, and calibration of the constant light power (I
PD
) feedback
circuits.
The LDC-3700C Series Laser Diode Controller implements a two-point calibration
for the Laser 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 Controller. The Laser Controller 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 Controller in the following manner for the Laser Controller
calibration:
1 Measure and record the resistance of a 1

, 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.
2 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. I is the actual Laser current in Amps.
3 The LASER output must be on in order to enter the LASER I calibration mode. Enter the
LAS:OUTPUT ON
command to turn the LASER output on.
4 d.Enter the LASER I calibration mode by issuing the
LAS:CAL:LDI
command. The TEC
display will blank and the LASER display will indicate a current in mA.
FUNCTION STATE GPIB COMMAND
LASER MODE I (constant current low bandwidth)
LAS:MODE:ILBW
RANGE low (lowest per instrument model)
LAS:RAN-x
LIMIT 90% of FS (full scale of range)
LAS:LIM:Ix
SET POINT 80% of FS (90% for LDC-3744C)
LAS:LDI