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
7/01
LDC-3700 Series
127
C H A P T E R
5
controller model you are calibrating (See Table 5.2 on page 115).
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
µ
A, the second set point will be about 1000
µ
A.) 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.
Laser Forward Voltage Measurement Calibration
The following procedure is for calibrating the LASER voltage measurement.
Configure the Controller in the following manner for the Laser Controller Voltage calibration:
1
With the LASER output off, connect a calibrated voltmeter, in parallel with a resistor (100
Ω
, 2 Watt for the LDC−3714B; 15
Ω
, 5 Watt for the LDC−3724B or LDC−3744B), to the
LASER output (Laser Anode and Laser Cathode) on the rear panel of the controller.
2
The LASER output must be on in order to enter the LDV calibration mode. Enter the
"LAS:OUT ON" command to turn the LASER output on.
FUNCTION
STATE
GPIB COMMAND
LASER MODE
I (constant current low bandwidth)
LAS:MODE:ILBW
RANGE
LDC−3714B
LDC−3724B
LDC−3744B
100 mA
500 mA
2000 mA
LAS:RANGE −1
LAS:RANGE −5
LAS:RANGE −1
LASER LIMIT
set to FS (full scale of range)
LAS:LIM:Ix
I Set POINT
LDC−3714B
LDC−3724B
LDC−3744B
60 mA
400 mA
400 mA
LAS:LDI 60
LAS:LDI 400
LAS:LDI 400
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