Laser Driver Current Calibration - Newport LDC-3706 Series User Manual

Laser Driver Current Calibration

The following procedure calibrates the laser constant current source for a single range and
modulation state. This procedure will need to be performed for each combination of laser driver
current range and modulation state. Since modulation state can be on or off, and there are three
laser current ranges, this procedure may need to be performed up to 6 times to completely
calibrate the system. If there is no intent to use any of the ranges or modulation states,
calibration may performed for only the combinations intended to be used. For example, if
modulation is not intended to be used, only the three current ranges for the instrument need to
be calibrated once each. During the calibration procedure the current is driven to two pre-
determined values. When each of these values is reached and is stable, the user enters the
actual value of the current, as measured by an external DMM. The LDC-3706 instrument then
automatically calibrates the laser diode current source and limits.
1. Measure and record the exact resistance of a resistor, using the chart below to
determine what type to measure based upon the unit:
LDC-3726
LDC-3736
LDC-37620
A 4-point probe resistance measurement is recommended.
2. Connect the appropriate resistor across the laser output terminals of the LDC-3706
instrument (pins {4, 5} for Laser Cathode (-) and {8, 9} for Laser Anode (+) on the 9-pin
connector or pins {A3, A4, 5} for Laser Cathode (-) and {A1, A2, 3} for Laser Anode (+)
on the 9W4 connector).
3. Navigate to the "LDI" selection in the Laser Calibration submenu of the laser parameter
menu tree.
Select the LDI calibration mode by pressing the SET button while the "LDI" selection is
displayed. Then, press the LAS button to start the calibration procedure. Calculate the
actual current output by using Ohm's Law:
Where V is the accurately measured voltage across the resistor with a precision
multimeter and R is the accurately measured load resistance.
Alternatively, an ammeter in series with the 1Ω resistor may be used to measure the
current.
4. Turn the ADJUST knob until the display shows the value of the laser current
measurement as calculated from step 4. Then press the LAS button.
5. The instrument will apply a new current after a short time. Repeat step 5 for the second
current.
6. Wait for the 7-segment display to exit the calibration mode. Once the self-calibration is
completed, the calibration constants will be stored to the non-volatile memory and the
display will return to its previous state.
December 2019
9 Pin Connector
1Ω, 25W
9 Pin Connector
1Ω, 25W
9W4 Pin Connector
0.1Ω, 100W
=
102 LDC-3706 Series Laser Controller