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Chapter 7
7.2.6
Remote Operation I
Calibration
where V is the measured voltage across the resistor, and R is the
measured load resistance.
b.
Go to the single module display by first pressing the MENU button,
then the Modules soft key, then the slot soft key that corresponds to the
module to be calibrated.
c.
Press the Setup soft key, change the Mode to Im (Photodiode constant
current mode), and set the laser current limit (Io Lim) to maximum.
Press the
soft key to return to the single display.
d.
Press the LDD ON key to turn the laser output on. If a laser on delay
has been set, wait that amount of time to allow the laser output to
engage.
e.
Go to the calibration display by first pressing the MENU button, then
the Config soft key, then the Cal soft key, then the channel to be
calibrated. At the calibration screen, press the Im soft key. Follow the
on-screen instructions to complete the calibration. The calibration can
be terminated without affecting the stored constants if the Term soft
key is pressed at any point prior to completing the calibration..
PD
a.
With the laser output off, connect a calibrated ammeter to the
photodiode anode output of the module and connect the circuit of
Figure 34 to the laser and photodiode outputs.
If a calibrated ammeter (with 0.1 µA resolution) is not available, place a
calibrated DMM (with 0.1 mV resolution) to measure the voltage
across the resistor, R3, as shown in Figure 34. Calculate the current in
the following steps by using Ohm's Law:
where V is the measured voltage across the resistor, and R is the
measured load resistance.
b. Select the channel via the LAS:CHAN command. Set the laser current
limit to full scale via the LAS:LIM:LDI command. Set the photodiode
current set point to ½ full scale via the LAS:MDI command. Place the
unit into constant photodiode current mode via the LAS:MODE:MDI
command.
c.
Enter the LAS:OUTPUT ON command to turn the laser output on.
Current Calibration
I = V / R
77
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