User’s Guide
Precision Current Source
LDX-3412
ILX Lightwave Corporation · 31950 Frontage Road · Bozeman, MT, U.S.A. 59715 · U.S. & Canada: 1-800-459-9459 · International Inquiries: 406-556-2481 · Fax 406-586-9405
ilx.custhelp.com · www.ilxlightwave.com
70001305 March 2011
TABLE OF CONTENTS
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Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Safety and Warranty Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
Safety Information and the Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
General Safety Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
Safety Symbols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
Safety Marking Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
Returning an Instrument . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
Claims for Shipping Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
Comments, Suggestions, and Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . .vii
Chapter 1
General Information
Product Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Specifications1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Chapter 2
Operation
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
AC Power Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
LDX-3412 Familiarization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Front Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power-up Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating MODE Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Current LIMIT Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output Current Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
OUTPUT Off/On Switch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fault Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rear Panel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5
6
6
6
6
7
7
7
8
LDX-3412
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i
TA B L E O F C O N T E N T S
Output Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Chassis GND Connector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Photodiode Feedback (PD) GAIN Adjustment . . . . . . . . . . . . . . . . . . . . . . . 9
Warm-up and Environmental Considerations . . . . . . . . . . . . . . . . . . . . . . . . . 9
Operating Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Connecting to Your Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
System Interlock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Photodiode Feedback Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Laser Diode Connections and Shielding . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Grounding Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
General Operating Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Chapter 3
Troubleshooting
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
ii
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LDX-3412
SAFETY AND WARRANTY INFORMATION
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The Safety and Warranty Information section provides details about cautionary
symbols used in the manual, safety markings used on the instrument, and
information about the Warranty including Customer Service contact information.
Safety Information and the Manual
Throughout this manual, you will see the words Caution and Warning indicating
potentially dangerous or hazardous situations which, if not avoided, could result in
death, serious or minor injury, or damage to the product. Specifically:
!
CAUTION
Caution indicates a potentially hazardous situation which can result in minor or
moderate injury or damage to the product or equipment.
WARNING
Warning indicates a potentially dangerous situation which can result in serious injury or
death.
WARNING
Visible and/or invisible laser radiation. Avoid direct exposure to the beam.
General Safety Considerations
If any of the following conditions exist, or are even suspected, do not use the
instrument until safe operation can be verified by trained service personnel:
• Visible damage
• Severe transport stress
• Prolonged storage under adverse conditions
• Failure to perform intended measurements or functions
If necessary, return the instrument to ILX Lightwave, or authorized local ILX
Lightwave distributor, for service or repair to ensure that safety features are
maintained (see the contact information on page vii).
All instruments returned to ILX Lightwave are required to have a Return
Authorization Number assigned by an official representative of ILX Lightwave
Corporation. See Returning an Instrument on page v for more information.
Safety and Warranty Information

iii
SAFETY SYMBOLS
SAFETY SYMBOLS
This section describes the safety symbols and classifications. Technical specifications
including electrical ratings and weight are included within the manual. See the Table of
Contents to locate the specifications and other product information. The following
classifications are standard across all ILX Lightwave products:
• Indoor use only
• Ordinary Protection: This product is NOT protected against the harmful ingress of moisture.
• Class I Equipment (grounded type)
• Mains supply voltage fluctuations are not to exceed ±10% of the nominal supply voltage.
• Pollution Degree II
• Installation (overvoltage) Category II for transient overvoltages
• Maximum Relative Humidity: <80% RH, non-condensing
• Operating temperature range of 0 ×C to 40 ×C
• Storage and transportation temperature of ñ40 ×C to 70 ×C
• Maximum altitude: 3000 m (9843 ft)
• This equipment is suitable for continuous operation.
Safety Marking Symbols
This section provides a description of the safety marking symbols that appear on the
instrument. These symbols provide information about potentially dangerous situations
which can result in death, injury, or damage to the instrument and other components.
or
(I)
iv

Caution,
refer to
manual
Earth
ground
Terminal
Alternating
current
Visible and/or
invisible laser
radiation
Caution, risk
of electric
shock
Protective
Conductor
Terminal
Caution, hot
surface
Frame or
chassis
Terminal
On: In position of a bistable push control. The
slash (I) only denotes that mains are on.
Safety and Warranty Information
or
(O)
Off: Out position of a bistable push control.
The circle (O) only denotes that mains are off.
WA R R A N T Y
WARRANTY
ILX LIGHTWAVE CORPORATION warrants this instrument to be free from
defects in material and workmanship for a period of one year from date of
shipment. During the warranty period, ILX will repair or replace the unit, at our
option, without charge.
Limitations
This warranty does not apply to fuses, lamps, defects caused by abuse,
modifications, or to use of the product for which it was not intended.
This warranty is in lieu of all other warranties, expressed or implied, including any
implied warranty of merchantability or fitness for any particular purpose. ILX
Lightwave Corporation shall not be liable for any incidental, special, or
consequential damages.
If a problem occurs, please contact ILX Lightwave Corporation with the
instrument's serial number, and thoroughly describe the nature of the problem.
Returning an Instrument
If an instrument is to be shipped to ILX Lightwave for repair or service, be sure to:
1
Obtain a Return Authorization number (RA) from ILX Customer Service.
2
Attach a tag to the instrument identifying the owner and indicating the required service or
repair. Include the instrument serial number from the rear panel of the instrument.
3
Attach the anti-static protective caps that were shipped with the instrument and place the
instrument in a protective anti-static bag.
4
Place the instrument in the original packing container with at least 3 inches (7. 5 cm) of
compressible packaging material. Shipping damage is not covered by this warranty.
5
Secure the packing box with fiber reinforced strapping tape or metal bands.
6
Send the instrument, transportation pre-paid, to ILX Lightwave. Clearly write the return
authorization number on the outside of the box and on the shipping paperwork. ILX
Lightwave recommends you insure the shipment.
If the original shipping container is not available, place your instrument in a
container with at least 3 inches (7.5 cm) of compressible packaging material on all
sides.
Repairs are made and the instrument returned transportation pre-paid. Repairs
are warranted for the remainder of the original warranty or for 90 days, whichever
is greater.
Safety and Warranty Information
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v
WA R R A N T Y
Claims for Shipping Damage
When you receive the instrument, inspect it immediately for any damage or
shortages on the packing list. If the instrument is damaged, file a claim with the
carrier. The factory will supply you with a quotation for estimated costs of repair.
You must negotiate and settle with the carrier for the amount of damage.
vi
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Safety and Warranty Information
WA R R A N T Y
Comments, Suggestions, and Problems
To ensure that you get the most out of your ILX Lightwave product, we ask that
you direct any product operation or service related questions or comments to ILX
Lightwave Customer Support. You may contact us in whatever way is most
convenient:
Phone . . . . . . . . . . . . . . . . . . . . . . . . . . . (800) 459−9459 or (406) 586−1244
Fax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (406) 586−9405
Email. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . support@ilxlightwave.com
Or mail to:
ILX Lightwave Corporation
P. O. Box 6310
Bozeman, Montana, U.S.A 59771
www.ilxlightwave.com
When you contact us, please have the following information:
Model Number:
Serial Number:
End−user Name:
Company:
Phone:
Fax:
Description or sketch of what
is connected to the ILX
Lightwave instrument:
Description of the problem:
If ILX Lightwave determines that a return to the factory is necessary, you are
issued a Return Authorization (RA) number. Please mark this number on the
outside of the shipping box.
You or your shipping service are responsible for any shipping damage when
returning the instrument to ILX Lightwave; ILX recommends you insure the
shipment. If the original shipping container is not available, place your instrument
Safety and Warranty Information
 vii
WA R R A N T Y
in a container with at least 3 inches (7.5cm) of compressible packaging material
on all sides.
We look forward to serving you even better in the future!
viii 
Safety and Warranty Information
CHAPTER
1
GENERAL INFORMATION
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This manual contains operation and maintenance information for the LDX-3412
Precision Current Source. Appendix A contains a brief troubleshooting guide.
Product Overview
The LDX-3412 is an easy to operate, precision current source. It is optimized for
driving laser diodes and LEDs with an output range of 0 to 200 mA, with a
compliance voltage of >6 volts. Multiple built-in protection features ensure that the
supply output is transient-free and bounded under all conditions. There are three
modes of operation for the LDX-3412: (1) Constant Power, which allows
photodiode feedback to control the output current; (2) Constant Current, in which
feedback from the laser is used to control the output current; and (3) Limit Display,
in which the current limit is displayed while the output current is off.
Features of the LDX-3412 include:
• Intuitive front panel layout
• Fully independent, precision current limit control
• Slow turn-on circuit for laser diode protection
• Safe OUTPUT off/on switch
• Double shielded transformers for low noise
• Photodiode feedback capability
LDX-3412
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1
CHAPTER
1
GENERAL INFORMATION
Product Overview
Specifications1
DRIVE CURRENT OUTPUT
Output Current Range:
0 to 200 mA
Compliance Voltage:
6.0 V
Temperature Coefficient:
<100 ppm/oC
Short Term Stability (1 hour):2
<50 ppm
Noise and Ripple:
<2 A rms
Transients:4
<100 A
DRIVE CURRENT LIMIT SETTINGS
Range:
1 to 200 mA
Accuracy:
+3 mA
PHOTODIODE FEEDBACK
Reverse Bias:
0 - 5V, adjustable
PD Current Input Range:
20 A to 2 mA
Stability:
5
+0.1%
MEASUREMENT (DISPLAY)
Display Type:
3-1/2 digit green LED
Output Current Range:
Output Current
Accuracy:6
0 to 199.9 mA
+0.2mA
LASER DIODE PROTECTION
Output Shorting Switch
Normally low impedance shunt
Output Enable Delay:
2s (per 21CFR 1040.10)
Current Limit:
Adjustable, redundant hardware limit
Error Monitoring / Reporting:
Current limit, open circuit
GENERAL
Power Requirements VAC:
90-125, 210-250 (50-60 Hz)
Size:
66mm x 140mm x 267mm; 2.6” x 5.5” x 10.5”
Weight:
1.8 kg; 4.0 lbs.
Operating Temperature:
0 oC to 50 oC
Storage Temperature:
-40 oC to 70 oC
Humidity:
<85% relative, non-condensing
Laser Safety:
Interlock, Output Delay (meets CDRH, US21, CFR 1040.10)
CONNECTORS
Current Source Output:
2
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LDX-3412
9-pin D-sub
PD Input:
9-pin D-sub laser connector
Chassis Ground:
4mm Banana Jack
Interlock:
9-pin D-sub laser connector
GENERAL INFORMATION
Product Overview
CHAPTER
1
1. All values relate to a two hour warm up period with output enabled.
2. Over 10 to 30 minutes, half−scale output @ 25oC ambient.
3. Half−scale output, measured electrically with a resistive load evaluating AC coupled rms value over a 100 kHz bandwidth.
4. Maximum output current transient resulting from normal operations (i.e. power on/off, current on/off), as well as accidental situations
(i.e. power line plug removal). Testing to ILX Technical Standard #LDC−00196.
5. Maximum monitor photodiode current drift over any 30 minute period. Assumes zero drift in photodiode responsivity.
6. Measured at 25oC.
Our goal is to make the best laser diode instrumentation available anywhere. To
achieve this, we need your ideas and comments on ways we can improve our
products. We invite you to contact us at any time with your suggestions.
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LDX-3412
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CHAPTER
4
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LDX-3412
1
GENERAL INFORMATION
Product Overview
CHAPTER
2
OPERATION
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This chapter is a guide to setting up and operating the LDX-3412. The controls
and connectors are described, and then step-by-step instructions for connecting
and using the LDX-3412 are presented.
Installation
Before plugging in the LDX-3412 to your AC power source, AC Power
Considerations . After power-up, make sure that the OUTPUT is off (LED unlit).
For operating procedure, see Operating Instructions on page 9.
AC Power Considerations
The LDX-3412 can be configured for operation with nominal line voltages of 100,
120, 220, and 240 VAC. The unit is configured at the factory for the appropriate
range. Make sure the AC input power matches the range marked on the rear
panel.
To avoid electrical shock hazard, connect the instrument to properly earth-grounded
electical supply only. Failure to observe this precaution can result in severe injury or
death.
LDX-3412 Familiarization
The following sections are provided to familiarize the user with features found on
the LDX-3412.
LDX-3412

5
CHAPTER
2
OPERATION
Installation
Front Panel
The LDX-3412 front panel is shown in Figure 2.1.
Figure 2.1 LDX-3412 Front Panel
Power-up Sequence
With the LDX-3412 properly connected to an AC power source, pressing the AC
POWER off/on switch causes the unit to initiate its power-up sequence. During
this period the output terminals are unconditionally shorted and the OUTPUT
off/on switch is inhibited for two seconds. This is done to prevent transients from
reaching your laser diode.
Operating MODE Selection
The MODE select switch allows the user to select between the three modes of
operation by turning the MODE knob to the desired mode. CONST P selects
constant power mode for photodiode feedback control. CONST I selects constant
current mode for normal operation. LIMIT DISPLAY selects a display mode in
which the output is turned off and the current LIMIT is displayed on the LED
display. When the MODE select switch is turned between modes, the output is
turned off.
Current LIMIT Adjustment
The current LIMIT knob allows the user to set the upper limit on output current.
The user may adjust the output current from zero (LIMIT knob fully counterclockwise CCW) to 200 mA (LIMIT knob fully clockwise CW). This LIMIT knob is
recessed to prevent accidental readjustment of the output current during
operation.
6

LDX-3412
OPERATION
Installation
CHAPTER
2
Under all modes of operation the output current is unconditionally limited to the
value set by the LIMIT adjustment.
Output Current Adjustment
The output current adjustment knob is located in the top right-hand corner of the
front panel. Turning this knob clockwise (CW) will increase the output current. The
output current will be displayed on the LED display during CONST P or CONST I
operation.
OUTPUT Off/On Switch
The OUTPUT off/on switch is located in the lower right-hand corner of the front
panel. This switch has a toggling action which turns the output current of the
LDX-3412 on and off. When the output is active, the LED indicator just above the
switch will be lit.
When the output is off, a low impedance shunt is activated across the output
terminals. In this state it is safe to connect or disconnect sensitive devices from
the LDX-3412, even though the power supply itself is on. When the LDX-3412 is
first turned on, the OUTPUT off/on switch is inhibited for several seconds. This
forces the internal, low impedance shunt to remain active across the output
terminals until the LDX-3412 control circuits are stabilized. Additionally, there are
four other conditions which will automatically cause the output to reset to the off
state:
• Power Drop-outs - AC line power drop-outs lasting more than about 10 msec will trigger an
internal power monitor and cause the output to switch unconditionally to the off state. This
sequence is also initiated when the LDX-3412 is switched off or unplugged.
• Open Circuit - If the compliance voltage of the externally connected circuit exceeds about 6
volts, the output is switched to the off state and the OPEN CKT indicator is activated. Most
commonly this occurs when the OUTPUT off/on switch is pressed without a load attached.
• Mode Changes - Changing the position of the MODE selector switch resets the output to
the off state.
• Interlock - If the interlock circuit is broken, the output is reset to the off state.
If any of these conditions occur, the output may be turned on again by simply
pressing the OUTPUT off/on switch, after corrective action is taken (if needed).
Fault Indicators
The LDX-3412 has two visual front panel fault indicators, OPEN CKT and LIMIT.
• OPEN CKT - indicates that the compliance voltage required at the LDX-3412 output
terminals has exceeded approximately 6 volts. Most commonly this happens when there is
no load attached to the output or the load becomes disconnected when the output is active.
When an OPEN CKT condition occurs, the LDX-3412 output is automatically turned off and
03_11
LDX-3412
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7
CHAPTER
2
OPERATION
Installation
the OPEN CKT indicator latches on. The OPEN CKT indicator will remain on until the
output is manually turned on again.
• LIMIT - indicates that the LDX-3412 output is being limited to the setting of the front panel
LIMIT knob. When a LIMIT condition occurs, the LIMIT indicator becomes lit.
The LIMIT DISPLAY indicator is not a fault indicator. It is lit when the unit is
operated in the LIMIT DISPLAY mode. This is done to remind the user that LIMIT
DISPLAY mode is in operation and the OUTPUT switch is inactive.
Rear Panel
The rear panel contains the 9-pin D-sub connector, chassis ground post,
photodiode gain adjustment controls, power cord receptacle, and serial number
sticker. .
Figure 2.2 LDX-3412 Rear Panel
1, 2
3
4, 5
6
7
8, 9
Interlock
Chassis Ground
Laser Cathode
PD Cathode (+)
PD Anode (-)
Laser Anode
1
2
6
7
3
4
8
9
5
Figure 2.3 D-connector (J105) Pinout
8
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LDX-3412
OPERATION
Installation
CHAPTER
2
Output Connectors
Output current is available from the 9-pin D-sub connector (J105). Pins 4 and 5
are the negative output, and pins 8 and 9 are the positive output current
connections. These pins are jumpered to provide greater contact area for the
output connections. This is done to reduce the risk of an open output connection
due to a loose connector. Thus, the output is made safer for laser diodes.
Note: Whenever external connections are made to the output at pins 4 and 5 and 8 and 9.
These connector leads must be jumpered as shown above to ensure the greatest laser
diode safety.
Chassis GND Connector
The output current terminals are floating with respect to chassis ground. A chassis
ground GND connector (bare metal) is available for the user's convenience. See
Section 2.5.4, Laser Diode Connections and Shielding.
Photodiode Feedback (PD) GAIN Adjustment
Photodiode feedback gain may be adjusted by the user via the COARSE and
FINE controls on the rear panel of the LDX-3412. When the CONST P mode is
selected, the user may adjust the feedback gain for proper testing of a laser diode.
Turning the COARSE and FINE controls counter-clockwise (CCW) will increase
the feedback gain and decrease the output current. See Figure 2.4 for setting the
photodiode feedback gain.
Warm-up and Environmental Considerations
The LDX-3412 should be operated at an ambient temperature between 0 and
50 oC. Storage temperatures should be in the range of -40 oC to 70 oC. In order to
achieve rated accuracy, the LDX-3412 should be warmed up for 1 hour before
use.
Note: To prevent overheating, the LDX-3412 must be kept well ventilated. Allow at least
1/2 inch clearance around the vent holes.
Operating Instructions
The following sections contain instructions on the set-up and operation of the
LDX-3412. Section 2.5.6 contains the step-by-step operating procedures. For
calibration, see Section 4.2.
Connecting to Your Device
When connecting laser diodes and other sensitive devices to the LDX-3412, we
recommend that the LDX-3412 be powered up and the OUTPUT be off (LED
unlit). In this condition a low impedance shunt is active across the output
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OPERATION
Installation
terminals. When disconnecting devices, it is only necessary to turn the OUTPUT
off.
System Interlock
When the LDX-3412 is shipped, an interlock is incorporated at connector J105
(pins 1 and 2). Output current will not flow unless there is an electrical connection
made between pins 1 and 2 of J105.
When the interlock function is to be used, the user must provide a normally closed
switch or relay across pins 1 and 2 of the 9-pin connector (J105). The switch must
be electrically isolated from all other circuits, including earth ground.
Photodiode Feedback Connections
The 9-pin connector J105 (see pinout, Figure 2.3) on the rear panel contains the
current supply output and earth ground. The photodiode feedback signal is input
at the connector at pins 6 and 7.
Many laser diode modules contain an internal photodiode that monitors the backfacet emission of the laser. This photodiode is usually internally connected to
either the laser anode or cathode. Figures 2.5 A - D show the recommended
connections and shielding for the various configurations of laser diode modules
and photodiode feedback schemes.
The feedback photodiode reverse-biasing supply shown in these figures must be
supplied by the user. You must locate this supply where it won't cause the
common mode voltage of the feedback inputs to exceed the specified maximum of
+6 V, relative to the "-" current output (J105, pins 4,5). Noise from this biasing
supply may contribute to the output noise levels; therefore, a battery with shielded
connections is recommended.
Module
OUTPUT
7
+
6
Bias
+
9
5
P. D.
L. D.
3
Earth Ground
Figure 2.4 Common Laser Cathode - Photodiode Cathode
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Module
OUTPUT
7
+
6
Bias
+
9
5
P. D.
3
L. D.
Earth Ground
Figure 2.5 Common Laser Cathode - Photodiode Anode
Module
OUTPUT
7
+
6
Bias
+
9
5
P. D.
3
L. D.
Earth Ground
Figure 2.6 Common Laser Anode - Photodiode Cathode
Module
OUTPUT
7
+
6
Bias
+
9
5
P. D.
L. D.
3
Earth Ground
Figure 2.7 Common Laser Anode - Photodiode Anode
If a feedback photodiode is used which is electrically isolated from the laser, the
feedback circuit must be resistively "tied" at some point to the output circuit. A
large resistance of 1 Mohm, connected from the laser cathode to the photodiode
anode, may be used in place of the direct connection. This is done to keep the
feedback inputs within the specified maximum +6 volt common mode voltage,
relative to the "-" laser current output terminal. The circuit of Figure 2.5 should be
used, if feasible.
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2
Laser Diode Connections and Shielding
Before connecting the laser diode to the LDX-3412, be sure that the front panel OUTPUT
switch is in the OFF position (LED unlit). Before turning on the OUTPUT, be sure that the
current LIMIT has been correctly set.
The LDX-3412 output is available through the 9-pin rear panel connector (J105).
The LDX-3412 sources current through pins 8 and 9 to the laser anode (+) and
returns current from cathode (-) through pins 4 and 5.
It is recommended that the connections to the LDX-3412 output be made using
twisted wire pairs with an earth-grounded shield (see Figures 2.4-2.7). The output
conductors are left floating relative to earth ground to suppress AC poweron/power-off transients that may occur through an earth-ground path. If the output
circuit is earth-grounded at some point (such as through the laser package and
mount), the user must be careful to avoid multiple earth grounds in the circuit.
Multiple earth grounds may provide circuit paths that induce spurious currents in
the photodiode feedback circuit and output leads.
Grounding Considerations
The outputs of the LDX-3412 are isolated from chassis ground allowing either
output terminal to be grounded at the user's option. Figures 2.4 - 2.7 show the
proper earth-ground shielding for the most common laser diode/photodiode
connections.
General Operating Procedure
The LDX-3412 can be operated in several modes. The following operating
procedure is applicable to most common usage.
12 
LDX-3412
1
Plug the LDX-3412 into a properly grounded, three-terminal AC power source which
supplies the correct voltage and frequency for your unit.
2
Turn on the LDX-3412; allow a one hour warm-up period for rated accuracy operation.
3
Select the LIMIT DISPLAY MODE and adjust the LIMIT knob to the maximum current that
you wish to source.
4
Select the desired MODE of operation.
5
With the OUTPUT off (LED unlit), make the necessary external circuit connections.
Double check to ensure that the correct polarity has been observed when connecting to
laser diodes or other devices which are sensitive to being reversed biased. For proper
photodiode feedback connections, refer to Section 2.5.3.
6
If the CONST P mode is selected, turn the COARSE and FINE PD GAIN pots fully
counter-clockwise (CCW). This will initially maximize the feedback gain and minimize the
OPERATION
Installation
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2
output current to the laser.
7
Switch the OUTPUT on (LED lit), and adjust the current to the desired DC level using the
main current setting knob.
Note: If there is no output current at this point, check to be sure that the proper interlock
connections have been made. If the interlock is enabled, Pins 1 and 2 of J105 must be
electrically connected before output current will flow.
In order to find the proper photodiode feedback gain for your laser (in CONST P mode), it
will be necessary to follow these additional steps:
8
With the output on, slowly turn the FINE control clockwise (CW) until the proper feedback
is reached. Turning the GAIN controls clockwise (CW) will increase the output current. If
the FINE control is turned fully clockwise but the proper gain has not been reached,
continue with Step 9.
9
Reset the FINE control to its fully counter-clockwise (CCW) position. Next, slowly turn the
COARSE control clockwise (CW) about 1/4 turn. If the LIMIT LED becomes lit, turn the
COARSE control back down (CCW) a bit. Then repeat Steps 8 and 9 as necessary.
Note: At any time during the operation of the LDX-3412, the output current limit setting
may be observed by selecting LIMIT DISPLAY mode. In this mode, the output current will
be off and the current limit setting will be displayed on the LED display.
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TROUBLESHOOTING

Calibration and line Voltage Selection require opening the case and exposure to
potentially lethal voltages. These procedures are to be performed by qualified
service personnel only. Consult the factory for service instructions.
ILX Lightwave provides in-house and on-site calibration services for ILX
instruments. Most ILX instruments require yearly calibration to ensure
performance to published specifications. ILX factory calibrations employ NIST
traceable measurement instrumentation, and our calibration engineers and
technicians use automated test equipment to accurately and efficiently capture
and record calibration data. An original certificate of calibration authenticity is
provided with all instrument calibrations, and a detailed report showing any precalibration out-of-tolerance conditions is available upon request. Calibration turntimes are normally five business days or less. On-site calibrations can be
performed around your production schedule, night or day, seven days a week.
Please contact ILX Customer Support (see page xi for contact information) for
additional calibration information.
Troubleshooting
This appendix is a guide to troubleshooting the LDX-3412. Some of the more
common symptoms are listed here, and the appropriate troubleshooting actions
are given. We recommend that the user start at the beginning of this guide. Read
the symptom descriptions, and follow the steps for the corrective actions which
apply. If you encounter problems which are beyond the scope of this
troubleshooting guide, contact ILX Lightwave at the number listed at the front of
LDX-3412

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CHAPTER
3
TR OUBLESHOOTING
Troubleshooting
this manual. Our Service Engineers will be glad to answer any questions
concerning this or any other ILX Lightwave product..
Table 3.1 Troubleshooting Symptoms and Actions
SYMPTOM
CORRECTIVE ACTIONS
LDX-3412 will not power up.
•
Check AC Power line voltage and power cord connection.
LDX-3412 powers up, but there is
no current OUTPUT.
•
Check the MODE switch. Output will only be on while in CONST I or
CONST P modes.
•
Check the interlock feature. If interlock is enabled, there must be a
short between pins 1 and 2 of J105 to have output.
•
Check the OUTPUT switch. The LED should be lit.
•
Check the OPEN CKTindicator. If it is lit, there is an open in the output
circuit.
•
Check the current output control knob. Set it fully counter-clockwise
(CCW) for minimum output.
•
If CONST P mode is used, check the feedback gain setting (Section
2.3.11). Try turning the feedback GAIN controls down (CCW).
•
If CONST P mode is used, check the feedback connections. Try
reversing the polarity of the photodiode.
•
Check the interlock circuit. A broken circuit will reset the LDX-3412 to
the off state.
•
Check that the AC power cord connection is secure. Power drop-outs
may turn the OUTPUT off.
•
Check the AC line cord to make sure that it is well-connected.
Output current at limit, cannot be
lowered
OUTPUT intermittently turns off
during operation.
16 
LDX-3412
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