ILX Lightwave LDC-3700C Series, Руководство пользователя, Страница: 169 / 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
153
C H A P T E R
5

I
PD
Current Calibration
The following procedure is for calibrating 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 LDC-3700C Series
Laser Diode Controller then automatically calibrates the LASER feedback circuits.
Configure the Controller in the following manner for the Laser Controller
calibration:
1 With the LASER output off, connect a calibrated ammeter to the PD Anode output of the
Laser Controller output connector (9 pin on rear panel), and connect the circuit of Figure
5.1 on page 137 to the LASER and PD outputs with the correct load resistor for the
controller model you are calibrating (See Table 5.2 on page 138).
2 Enter the
LAS:OUT ON
command to turn the LASER output on. Verify proper operation,
i.e., the I
PD
output should be close to the set point (read it via the
LAS:MDI?
query), and
the unit should not be in current limit (read the limit status via the
LAS:COND?
query, bit
0).
3 Enter the
LAS:CAL:MDI
command to place the Controller in its LASER Current
Calibration mode. The controller will increase the laser current output until the current at
the PD monitor (I
PD
) inputs equals the targeted set point.
4 After a few seconds, the Controller will be ready for the actual I
PD
current to be entered via
the
LAS:MDI <nrf value>
command. The measured value of the current should not
be entered until the Controller is ready to receive it. The Controller will be ready to
receive the current value when, after a
LAS:CAL:MDI?
query is sent, the response from
the Controller is "1".
5 Once the actual I
PD
value is entered via the
LAS:MDI <nrf value>
command, the
Controller will store the new calibration value in non-volatile memory. It will then set the
output to approximately one-fourth (1/4) of the original current. (For example, if the first
calibration set point was 4000 µA, the second set point will be about 1000 µA.) Then, it
will be ready to receive the second calibration value.
6 Input the second actual (measured) monitor diode current (as an <nrf value>).
7 Once the second actual I
PD
value is entered via the
LAS:MDI
command, the new
calibration constants will be calculated and stored into non-volatile memory. The
*OPC?
query may be used (after the
LAS:MDI
value is sent) to determine when the calibration is
completed.
FUNCTION STATE GPIB COMMAND
PD BIAS VOLTAGE POT >3.5V
LASER MODE P (constant power)
LAS:MODE:MDP
CAL PD set equal to zero
LAS:CALMD
LASER LIMIT 90% of FS (full scale of range)
LAS:LIM:Ix
I
PD
Set POINT 4000

A
LAS:MDI