CALIBRATION AND TROUBLESHOOTING
Laser Diode Current Setpoint Calibration
126 LDX-36000 Series
CHAPTER 6
Laser Diode Current Setpoint Calibration
1 Set the 36000 output mode to CW with the following GPIB command: LAS:MODE:CW
2 Set the current calibration to default values by sending the following command:
LAS:CAL:LDI 1,0
3 Use a shorted output cable to connect the 36000 current output to a high accuracy current
transducer.
4 Set the current limit to the maximum value for the instrument.
5 Set the current setpoint to 20% of the maximum value for the instrument with the following
command: LAS:LDI setpoint
- where "setpoint" is the current value in amps
6 Turn the 36000 current output on with the following command: LAS:OUT ON
7 Record the value of current measured by the current transducer.
8 Set the current setpoint to 80% of the maximum value for the instrument with the following
command: LAS:LDI setpoint
- where "setpoint" is the current value in amps
9 Record the value of current measured by the current transducer.
10 Calculate the slope and offset of the CW current setpoint with the following equations:
slope = (36000 80% setpoint - 36000 20% setpoint ) / ( Transducer 80% measurement -
Transducer 20% measurement )
offsetAmps = 36000 80% setpoint - ( slope * Transducer 80% measurement )
Convert the offset in terms of amps to offset in terms of DAC counts.
offsetDacCounts = 65,535 / ( 1.1 * MAX QCW CURRENT )
11 Send the CW current setpoint calibration to the 36000 using the following command:
LAS:CAL:LDI slope,offsetDacCounts
12 Set the current setpoint to 50% of the maximum value for the instrument with the following
command: LAS:LDI setpoint
- where "setpoint" is the current value in amps
13 Record the value of current measured by the current transducer.
14 Verify that the current setpoint is within the accuracy specifications of the instrument.
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