f
Release the (PARAMETER) SET switch to store the first calibration value into non-volatile memory.
It
will then set the second calibration current, approximately one-fourth of the original current. (For
esample,
if
the first calibration set point was
4000
PA,
the second set point will
be
about 1000
PA.)
Calculate the second current as in Step a.
g
The LDC-3700 Series Laser Diode Controller will beep when
it
is ready to accept the second calibration
value. When it does, press and hold in the (PARAMETER) SET switch and turn the ADJUST knob until
the LASER display indicates the same current as calculated in Step f.
I.
Release the (PARAMETER) SET switch to accept the second calibration point. After the (PARAMETER)
SET switch is released, the LDC-3700 Series Laser Diode Controller will calculate the calibration
constants, store them to nonvolatile memory, beep, and return to its former (before calibration) state.
6.4.4
Remote Opration
I,,
Current
Calibration
Thc following procedure is for calibrating the LASER
I,,
constant current source. This procedure calibrates the
fecdback circuits for constant I,, and constant
P,,
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-3700 Series Laser Diode
Controller
then automatically calibrates the LASER feedback circuits.
This procedure is for remote
(GPIB)
operation. See Section
6.4.3
for local calibration of the
I,,
current.
a.
With the LASER output off, connect a calibrated ammeter to the PD Anode output of the LDC-3700
Series Laser Diode Controller, and connect the circuit of Figure
6.1
to the LASER and PD outputs
(R3
=
1
n.
LDC-3742B;
11
Q,
LDC-3722B; or
49
R,
LDC-3712).
If
a calibrated ammeter (with
0.1
pA
resolution) is not available, use a zero-Ohm jumper in place of the
;trnrneter Then. place a calibrated DMM (with 0.1 mV resolution) to measure the voltage across the
resistor. R1. as shown in Figure
6.1.
Calculate the current in the following steps by using Ohm's Law:
-\\here E is the accurately measured voltage across the resistor, and R is the accurately measured load
resistance. (A I-point probe resistance measurement is recommended.)
b
Set the
LASER
current limit via the "LAS:LIM:Ix" (where x
=
1,
2,
3,
or
5,
depending on the model and
range --sce
LAS:LIM
commands, Chapter 4) command as desired. Set the I,, set point to 4000
PA
via the
"LAS:MDI
1000"
command. Set the
CAL
PD parameter to zero via the "LAS:CALMD 0" command. This
puts the LDC-3700 Series Laser Diode Controller into a constant
I,,
(MDI)
mode.
c
Enter the "LAS:OUT ON" command to turn the LASER output on. Verify proper operation, i.e., the
I,,
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).
d
Enter the "LAS:CAL:MDI" command to place the LDC-3700 Series Laser Diode Controller in its LASER
Current Calibration mode.
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