ILX Lightwave LDC-3700C Series, Руководство пользователя, Страница: 158 / 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
142
LDC-3700C Series
C H A P T E R
5

Local Calibration of the Laser Current Source
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 80% and 20% 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 output of the current source.
Current Source Calibration
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 Laser Controller in the following state:
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.
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.
3 Press the ( LASER MODE ) ON switch to turn the LASER output on. The LASER output
must be on in order to enter the LASER I calibration mode.
Function State
Laser Mode I (constant current low bandwidth)
Range low (lowest per instrument model)
Limit 90% of FS (full scale of range)
Set Point 80% of FS (90% for LDC-3744C)