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www.teamWavelength.com
13
QCL OEM SERIES LOW-NOISE DRIVER
TROUBLESHOOTING
PROBLEM
POTENTIAL CAUSES
SOLUTIONS
Driver will not switch on
Improperly configured power
supplies
Carefully check the wiring diagram in
Figure 2 on page 2
. Make sure the
power supply polarity is not reversed. The FAULT LED will illuminate red if
the driver is switched on with reversed power supply polarity.
Internal fuses are blown
In an ESD-safe environment, open the QCL driver chassis and verify the
fuses are not blown. Replace the fuses if necessary. Refer to
page 15
.
Output will not enable
Improperly configured Remote
switches on the QCL unit
Make sure that the Remote switches in the QCL driver are set to the correct
position for your application. Refer to
Configure Local vs. Remote Control
on page 11
.
Remote Enable signal is not
correct
If the driver is configured to reference the Remote inputs, make sure the
signals are correct. Disconnect the remote input lines and check them
independently of the driver. Refer to
Table 1 on page 3
.
The QCL driver detected a
power supply fault
If the red FAULT LED is illuminated, the protection circuitry has detected a
fault condition on the power supply inputs. Refer to
Recover from a Power
Supply Protection Circuit Fault on page 12
.
The QCL driver detected an
over-temperature condition
If the red FAULT LED is illuminated and the signal on J1:7 is HI, the
protection circuitry has detected an over-temperature fault condition. Refer to
page 12.
Noise current is higher than
expected
There may be ground loops
in the system; some system
components may be higher
noise than expected; cabling
and shielding may be
inadequate
Refer to Wavelength Electronics Application Note
AN-LD08: “Manage
Grounding to Minimize Noise with the QCL Drivers”
:
https://www.teamwavelength.com/download/applicationtechnotes/an-ld08.pdf
Also reference
AN-LD09: “Troubleshooting Low Noise Systems”
:
https://www.teamwavelength.com/download/applicationtechnotes/an-ld09.pdf
Switching power supplies may
be noisy
Use the best quality switching power supplies you can find. We test our QCL
drivers using our stock PWRPAK-24V power supplies.
The output switched off
unexpectedly
The QCL driver detected a
power supply fault
If the red FAULT LED is illuminated the protection circuitry has detected a
fault condition on the power supply inputs. Refer to
Recover from a Power
Supply Protection Circuit Fault on page 12
.
The QCL driver detected an
over-temperature condition
If the red FAULT LED is illuminated and the signal on J1:7 is HI, the
protection circuitry has detected an over-temperature fault condition.
Laser output power lower
than expected
Current limit set too low
Using a test load (see
Figure 3 on page 2
) follow the procedure to set
the current limit (
page 9
). Verify that the current limit is suitable for your
laser by connecting the voltmeter across R
LOAD
; calculate the drive current
using Ohm’s Law (V = I * R).
20 kHz noise is in the output
current
QCL driver is operating in
current limit
If safe for the quantum cascade laser, increase the output current limit
setting. When actively operating in current limit, the safety circuits add noise
to the output.
If I run my QCL at about
5% of maximum output
current, the transfer function
becomes non-linear and I
see distortion in my output
current waveform.
QCL driver resolution is too low
Select a QCL driver with a much lower maximum output current. For
example, to run 50 mA, request a QCL125 (125 mA maximum output).
