C A L I B R A T I O N A N D T R O U B L E S H O O T I N G
Troubleshooting Guide
78
LDC-3926339
C H A P T E R
5
Automatic Shut Off Conditions
When the laser output is off, an internal short is placed across the laser output
(pins A2 and A3). By default, the current source output is turned off when when
you power up the mainframe. With the laser output enabled, the Channel or Status
screens indicate the measured laser current. If the output is not functioning or an
error code appears, check the following conditions or Table 5.7 on page
80
.
These conditions automatically force the laser current source to turn off:
•
Laser High Power Limit (Plim)
•
Laser High Voltage Limit (Vlim)
•
Laser Enable Interlock
•
Laser Enable Key Lock turned off on the front panel
•
Laser Open Circuit
In addition, the laser current limit setting (Ilim) clips the laser drive current at the
Ilim setpoint when the signal is being modulated or the current limit setting is
exceeded. When the laser current limit (Ilim) is reached, a current limit warning
appears on the CHAN menu. The current limit setting is independent of the
voltage drop of the device connected to the laser output. Since the current limit
circuitry is fully independent of the main current control, the current limit is safely
adjustable, even while the laser output is active.
The module's response to sensing the various limits is controlled through the
GPIB interface. Most high limit responses are set to turn off the source or give a
limit warning through the GPIB interface. See the LASER:ENAB:OUTOFF
command on page
49
for more information.
Output exceeds Power Limit
•
Make sure the output-off feature is not disabled. When
the power limit is exceeded the output is turned off, but
this feature can be disabled through the GPIB. At
power-up, the instrument defaults to this safety feature.
•
The "Power Limit" is not a hardware limit. It only serves
as a warning that the power measurement has
exceeded the limit set point.
Open Circuit Error occurs during calibration
•
Check load connections. Check that measuring meter
does not auto-range (use non-auto-ranging modes).
Calibration is aborted unintentionally
•
Calibration modes will be aborted if an open circuit is
detected or if entered measurements are invalid.
Table 5.5
Troubleshooting
Symptom
Corrective Action
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