M A I N T E N A N C E
Calibration Adjustments
26
LDT-5525
C H A P T E R
3
•
Set the current limit (I LIMIT) to 90% of full scale (e.g., 900 mA for 1000 mA range on the
LDX-3545), set the mode to I CW, set the output range as desired, and current set point to
80% of full scale (i. e. 800 mA for 1000 mA range on LDX-3545).
Disconnect any laser from the output. Connect a calibrated DMM across the LASER output
terminals and measure the current directly.
OR - Connect a 1
Ω
, 20 W, (LDX-3525 or LDX-3545) or 5
Ω
, 20 W, (LDX-3565) resistor
across the LASER output terminals and use a calibrated DMM to measure the voltage across
the resistor.
Calculate the current in the following steps by using Ohm's Law:
I = E / R
-where E is the accurately measured voltage across the resistor, and R is the accurately
measured load resistance. (A 4-point probe resistance measurement is recommended.)
•
Enter calibration mode by pushing the OUTPUT ON and ADJUST ENBL switches at the
same time for one second. The display will blank for two seconds and then turn the output on
(if it is not already on) and indicate output current in mA.
•
Let the current settle for about two minutes until the measurement indicates that it is stable to
five digits. Then, press and hold in the ADJUST ENBL switch and turn the ADJUST knob until
the display indicates the same current as measured on the DMM or as calculated in Step a (if
a voltage measurement is made).
•
Release the ADJUST ENBL switch to accept the first calibration point. After the ADJUST
ENBL switch is released, the LDX-3500 Series Precision Current Source will apply the
second calibration current, approximately one-fourth of the original current. (For example, if
the first calibration set point was 800 mA, the second set point will be about 200 mA.)
•
If a voltage measurement is used, calculate the second current as in Step a.
•
Press and hold in the ADJUST ENBL switch and turn the ADJUST knob until the LASER
display indicates the same current as shown on the DMM or calculated in Step e (if a voltage
measurement is used).
•
Release the ADJUST ENBL switch to accept the second calibration point. After the ADJUST
ENBL switch is released, the LDX-3500 Series Precision Current Source will calculate the
calibration constants
Then, the LDX-3500 Series Precision Current Source will automatically perform a current
limit calibration, which takes about 10 seconds (for IHBW mode) or 20 seconds (CW mode).
During this calibration the output will be driven to about 80% and then 20% of full scale. No
user input is required for the limit calibration.
After the limit is calibrated, the LDX-3500 Series Precision Current Source will store all the
calibration constants into non-volatile memory and then return to its former (before
calibration) state. The output remains on after calibration.
•
Repeat this procedure with the high bandwidth (I HBW), and then repeat it all with other
range (four combinations are possible).
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
