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9
QCL OEM SERIES LOW-NOISE DRIVER
WIRE THE POWER SUPPLIES
Wire the QCL driver to the dual power supplies as shown in
Figure 4
. If you are using the PWRPAK-24V power supplies
from Wavelength, we recommend you also use the wiring
kits WCB312 and WCB313.
AC(L) AC(N)
FG
-V
+V
AC(L) AC(N)
FG
-V
+V
POSITIVE SUPPLY
NEGATIVE SUPPLY
V- (Pin J4-2)
V+ (Pin J4-3)
Ground
(Pin J4-1)
Ground Interconnect
Neg-to-Pos Interconnect
Ground Wire
Twisted Pair
Chassis
Ground
150k
Ω
Earth
Ground
1
1
1
1
2
2
2
1. Cable included as part of the WCB312 Power Supply Wiring Kit
2. Included with the QCL Driver.
Connect to AC Mains; refer to power supply
specifications for input voltage requirements.
Figure 4. QCL Power Supply Wiring
Follow these instructions to wire the power supplies using
the WCB312 and WCB313. The same method applies to
connect other power supplies to the QCL driver.
•
The AC Line (black) and Neutral (white) wires: 24 AWG
black and white wires, 10” with ring lugs unattached but
included in kit: connect the AC Line wire to the AC(L)
terminals and the Neutral wire to the AC (N) terminals,
as shown in
Figure 4
.
•
AC Safety Ground #1: 24 AWG green wire, 10” with
ring lugs on each end; connect to the Frame Ground
terminals on the power supplies.
•
AC Safety Ground #2: 24 AWG green wire; 10” with one
ring lug; connect to the Frame Ground terminal on one
power supply; connect the other end to Earth Ground
(usually through the equipment rack, chassis, or optical
bench).
•
Common Ground: 24 AWG black wire; 10” with ring lugs
on each end; connect between V– of Positive Supply
and V+ of Negative Supply.
• Use the remaining ring lugs to connect the power
supply cable (WCB313) to the V+, Power Ground, and
V– terminals of the power supplies. See
page 20
for
information on the WCB313 cable.
Figure 4
indicates a 150 kΩ resistor connecting the
power supplies to ground; this resistor is necessary if the
electronics ground is tied to earth ground at some point
within your system, such as at a DAQ card, computer, or
USB cable connection.
This resistor provides a lossy connection from system
ground to earth ground, and will prevent the ground
potential of isolated power supplies from drifting. NOTE:
Some systems can have problematic ground loops. If this
occurs, you may want to try and optically isolate the remote
POWER and ENABLE lines. It is not a requirement for low
noise operation, but it can be an option. (See
Table 4
for
the remote Switch Settings.)
NOTE: For remote operation the front panel Power and
Enable switches must be on.
If you are unsure whether to include this resistor in your
system, contact Wavelength Electronics for technical
assistance.
CONNECT THE TEST LOAD
It is very important to configure the QCL driver using a
test load rather than the actual quantum cascade laser.
Refer to
page 2
for test load specifications and wiring
instructions. Connect the test load now.
SET THE CURRENT LIMIT
The QCL driver employs a soft-clamping current limit. The
limit circuit begins to act at a current below the absolute
limit setpoint, and will prevent the output current from ever
exceeding the absolute limit setpoint.
We recommend that setpoint is below 85% of the
current limit, because the noise level introduced into
the QCL rises when operating close to the current limit.
First, zero the SET and LIMIT currents by turning the
trimpots counter-clockwise; 21 turns for the SET trimpot
and 12 turns for the LIMIT trimpot.
Next switch on the power supplies, then switch on the
QCL driver by setting the POWER switch to ON (right); the
blue POWER LED on the front panel will illuminate. Do not
enable the output at this time.
The current limit is set using the LIMIT trimpot on the front
panel:
•
Refer to the datasheet for your QCL to find the maximum
current, then calculate the Current Limit Monitor voltage,
referencing
Table 3
for the transfer function:
V
I_LIM_MON
= I
LIMIT
/ Transfer Function
