74 Chapter 6 Calibration
the calibration mode and then process the command(s).
The *
OPC?
query may be used to determine when the calibration is
completed.
The operation complete flag (bit 0 of the Standard Event Status
Register) may be used to trigger an interrupt. This type of interrupt is
enabled by setting bit 0 of the Service Request Enable register and
using the
*OPC
command.
6.2.5 Local Operation I
PD
Current Calibration
This procedure calibrates the feedback circuits for constant I
PD
and constant P
PD
modes. The user enters the actual value of the current, as measured by an external
DMM. The 8000 then automatically calibrates the laser feedback circuits. MOPA
modules have photodiode feedback circuits on channel B only.
The I
PD
calibration circuit is diagrammed below. Use Table 10 above to select a
value for the R2 resister that matches the maximum drive current of the laser diode
module.
R1
100
R2
NEC PS2501-1
R3
100
V
A
Ipd Current
Ammeter
Voltmeter
4,5
8,9
6
7
LD Cathode
PD Anode
LD Anode
PD Cathode
9 Pin D-Sub
4
3
1
2
Figure 30 - I
PD
Calibration Circuit
a. With the laser output off, connect a calibrated ammeter to the PD
Anode output of the module and connect the circuit of Figure 30 to the
laser and PD 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 30. Calculate the current in
the following steps by using Ohm's Law:
I = V / R
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