MKS Oriel Instruments 3502 User manual

MKS Newport Family of Brands –ILX Lightwave®• Corion®• New Focus™ • Oriel®Instruments • Richardson Gratings™ • Spectra-Physics®
P/N: 90068136 REV: B, 8/12/2022
Optical Chopper System
User’s Manual
Oriel®Instruments
Model 3502, 3502-BASE

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Optical Chopper System
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Table of Contents
1Safety Precautions 6
1.1 Definitions and Symbols..................................................................................... 6
1.1.1 General Warning or Caution....................................................................... 6
1.1.2 Electrical Shock .......................................................................................... 6
1.1.3 European Union CE Mark .......................................................................... 7
1.1.4 On................................................................................................................ 7
1.1.5 Off............................................................................................................... 7
1.1.6 Waste Electrical and Electronic Equipment (WEEE)................................. 7
1.2 Warnings and Cautions....................................................................................... 8
1.2.1 General Warnings ....................................................................................... 8
1.2.2 General Cautions......................................................................................... 8
1.3 Location of Labels and Warnings..................................................................... 10
1.3.1 Model 3502 Optical Chopper Controller Rear Panel................................ 10
2General Information 11
2.1 System Overview.............................................................................................. 11
2.1.1 Key Product Features:............................................................................... 11
2.2 Scope of this Manual ........................................................................................ 11
2.3 Unpacking and Inspection ................................................................................ 12
2.3.1 What is included ....................................................................................... 12
2.4 Environmental Operation Requirement............................................................ 13
2.4.1 Operating Limits....................................................................................... 13
2.4.2 Weight and Dimensions............................................................................ 13
3Using the Chopper 14
3.1 How the Model 3502 Optical Chopper Works................................................. 14
3.2 Mounting the Unit............................................................................................. 15
3.2.1 Chopper Head ........................................................................................... 15
3.2.2 Chopper Motor.......................................................................................... 17
3.2.3 Mounting a Wheel..................................................................................... 17

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3.2.4 Mounting the Wheel Cover....................................................................... 19
3.3 Initial Setup....................................................................................................... 20
3.3.1 Power ........................................................................................................ 20
3.3.2 Connecting the Chopper Head to the Chopper Controller........................ 21
3.3.3 Connecting the Chopper Controller to a Computer via USB ................... 21
3.4 Operation .......................................................................................................... 21
3.4.1 Front Panel Operation............................................................................... 21
3.5 Back Panel Operation ....................................................................................... 28
4Computer Interfacing 30
4.1 Introduction....................................................................................................... 30
4.2 Using the Graphical User Interface (GUI)........................................................ 30
4.2.1 A Quick Start: How to Use the ‘New Focus Chopper Application’......... 31
4.3 USB Communication........................................................................................ 32
4.4 Command Index and Conventions.................................................................... 32
4.5 Command Description...................................................................................... 34
5Troubleshooting 41
5.1 Normal Startup Operation................................................................................. 41
5.2 Symptoms and Steps to Follow ........................................................................41
6Specifications 43
6.1 Chopping Frequency......................................................................................... 43
6.2 Internal Synthesizer .......................................................................................... 43
6.3 Reference Input................................................................................................. 43
6.4 Reference Output.............................................................................................. 44
6.5 Phase Shifter ..................................................................................................... 44
6.6 Harmonic Locking............................................................................................ 44
6.7 External Voltage Control.................................................................................. 44
6.8 General.............................................................................................................. 44
7Maintenance, Warranty, and Service 45
7.1 Enclosure Cleaning........................................................................................... 45
7.2 Warranty and Service........................................................................................ 45

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7.3 Request for Assistance / Service....................................................................... 46
7.4 Repair Service................................................................................................... 46
7.5 Non-Warranty Repair ....................................................................................... 47
7.6 Warranty Repair................................................................................................ 47
7.7 Loaner / Demo Material.................................................................................... 48

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Figures
Figure 1: Exclamation symbol........................................................................... 6
Figure 2: Electrical Shock symbol..................................................................... 6
Figure 3: CE mark.............................................................................................. 7
Figure 4: ON symbol. ........................................................................................ 7
Figure 5: OFF symbol........................................................................................ 7
Figure 6: WEEE Directive symbol.................................................................... 7
Figure 7: Warning, Certification, and Information Label................................ 10
Figure 8: Functional block diagram for Model 3502 Optical Chopper........... 14
Figure 9: Model 3502 Optical Chopper Head with wheel cover installed. ..... 16
Figure 10: Dimensions of Model 3502 Optical Chopper Head....................... 17
Figure 11: Chopper wheels.............................................................................. 18
Figure 12: Model 3502 Optical Chopper Controller front panel.................... 21
Figure 13: Model 3502 Optical Chopper Controller back panel. ................... 28
Figure 14: Model 3502 Optical Chopper Application window...................... 31

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1 Safety Precautions
1.1 Definitions and Symbols
The following terms and symbols are used in this manual.
1.1.1 General Warning or Caution
Figure 1: Exclamation symbol.
The Exclamation symbol in the figure above appears in Warning and Caution
tables throughout this manual. This symbol indicates that you should read the
associated documentation to determine the nature of any potential hazards and
any actions that should be taken against these hazards.
1.1.2 Electrical Shock
Figure 2: Electrical Shock symbol.
The Electrical Shock symbol in the figure above appears throughout this manual.
It indicates a hazard arising from dangerous voltage. Any mishandling could
result in irreparable damage to the equipment, and personal injury or death.

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1.1.3 European Union CE Mark
Figure 3: CE mark.
The presence of the CE Mark on Newport equipment means that this instrument
has been designed, tested and certified compliant to all applicable European
Union (CE) regulations and recommendations.
1.1.4 On
Figure 4: ON symbol.
The symbol in the figure above represents a power switch position on the Model
3502 Optical Chopper Controller. This symbol represents a Power On condition.
1.1.5 Off
Figure 5: OFF symbol.
The symbol in the figure above represents a power switch position on the Model
3502 Optical Chopper Controller. This symbol represents a Power Off condition.
1.1.6 Waste Electrical and Electronic Equipment (WEEE)
Figure 6: WEEE Directive symbol.
This symbol on the product or its packaging indicates that the product must not
be disposed with regular waste. It is the user’s responsibility to dispose of waste
equipment marked with the WEEE Directive Symbol accordingto local laws. The
separate collection and recycling of WEEE waste at the time of disposal will help
conserve natural resources and ensurethat it is recycled ordisposed of in a manner
that protects human health and the environment. For information about where the

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user can drop off WEEE waste for recycling, please contact your local Newport
representative.
1.2 Warnings and Cautions
1.2.1 General Warnings
Observe these general warnings when operating or servicing this equipment:
•Thoroughly read and understand this User’s Manual.
•Heed all warnings on the unit and in the operating instructions.
•Use this equipment indoors only.
•The external input power to this equipment can be up to 240 VAC. Please
follow this User’s Manual for proper use or installation of this instrument.
•Disconnect power before cleaning the equipment. Do not use liquid or
aerosol cleaners; use only a damp lint-free cloth.
•Lockout all electrical power sources before servicing the equipment.
•There are no user-replaceable fuses in this equipment. The user must
ensure that appropriate current-limiting protection is provided by the
external AC power line.
•Do not operate this equipment in an explosive or flammable atmosphere.
•Use only the supplied mains power cord with the external AC supply. Use
of under-rated power cords may cause property damage.
1.2.2 General Cautions
Observe these cautions when operating this equipment:
•Thoroughly read and understand this User’s Manual.
•If this equipment is used in a manner not specified in this manual, the
protection provided by this equipment may be impaired.
•Do not block ventilation openings.
•Use only the specified replacement parts.
•Follow precautions for static sensitive devices when handling this
equipment.
•This product should only be powered as described in the manual.
•There are no user-serviceable parts inside the Model 3502 Optical
Chopper Controller or motor head.

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WARNING
If this equipment is used in a manner not specified in this manual, the
protection provided by this equipment may be impaired.
WARNING
This instrument is intended for use by qualified personnel who recognize
thermal, shock, or laser hazards and are familiar with safety precautions
required to avoid possible injury. Read this User’s Manual thoroughly
before attempting to use the Model 3502 Optical Chopper!
CAUTION
The Model 3502 Optical Chopper is designed to be safe when operated
under Normal Environmental Conditions as defined in EN61010-1:2010.
Operation under harsher environmental conditions can result in severe
injury.
The Model 3502 Optical Chopper is intended for use in an industrial
laboratory environment. Use of this product in other environments, such
as residential, may result in electromagnetic compatibility difficulties due
to conducted as well as radiated disturbances.

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1.3 Location of Labels and Warnings
1.3.1 Model 3502 Optical Chopper Controller Rear Panel
Figure 7: Warning, Certification, and Information Label.

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2 General Information
2.1 System Overview
The Model 3502 Optical Chopper is used to introduce a periodic interruption of a
light path in an optical experiment resulting in an amplitude modulation, which is
useful for many small optical signal detection schemes. The modulation frequency
can be controlled from 4 Hz to 10.65 kHz. Full control is available through the
Model 3502 Optical Chopper Controller’s front panel. In addition, the Chopper
Controller can be programmed over a USB communication interface to set and
measure the modulation frequency, adjust the interruption phase, and perform all
other operations available through the front panel.
2.1.1 Key Product Features:
A number of advanced features make the Model 3502 Optical Chopper an
excellent choice for many applications:
•Extremely low jitter noise across entire range of chopping frequencies
•Windows-based graphical user interface (GUI)
•User-written software control
•LabVIEWTM and C# examples
2.2 Scope of this Manual
Carefully read this User’s Manual before using the 3502 Optical Chopper.
Be especially careful to observe the warnings and cautions throughout this
manual. If any operating instructions are not clear, please contact Newport.
This instruction manual contains the necessary information for operation and
maintenance of the Model 3502 Optical Chopper, as well as information for
troubleshooting and obtaining service if necessary.

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2.3 Unpacking and Inspection
WARNING
Do not attempt to operate this equipment if there is evidence of shipping
damage or you suspect the unit is damaged. Damaged equipment may
present additional hazards to you. Contact Newport technical support
for advice before attempting to plug in and operate damaged equipment.
The Model 3502 Optical Chopper is carefully assembled, tested, and inspected
before shipment. Upon receiving this instrument, check for any obvious signs of
physical damage that might have occurred during shipment. Report any such
damage to the shipping agent immediately.
NOTE: Retain original packing materials in case reshipment becomes necessary.
2.3.1 What is included
The 3502 package contents:
•Model 3502 Optical Chopper Controller.
•Model 3502 Motor Assembly (including wheel cover) with a shielded
Ethernet cable and a set of 2-slot, 7/5-slot, 42/30-slot, 60-slot, 60/2-slot,
and 100-slot wheels, and lab post mounting hardware. Wheels not
included in 3502-BASE model, and must be ordered separately.
•USB Flash Drive which contains this User Manual, USB driver, GUI
software application and documented programming examples.
•Power supply cables (North American and European).

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2.4 Environmental Operation Requirement
2.4.1 Operating Limits
Parameter
Minimum
Maximum
Voltage Requirements
100V/50-60Hz
240V/50-60Hz
Electrical Ratings
25 Watts
100-240 VAC
50-60 Hz
Operating temperature
10 °C (≤ 90% humidity, non-
condensing)
40 °C (≤ 90 % humidity,
non-condensing)
Storage temperature
0 °C (≤ 85% humidity, non-
condensing)
50 °C (≤ 85 % humidity,
non-condensing)
Relative Humidity (storage)
≤ 85%
Altitude
< 3000 meters (10000 feet)
Environment, Use
Indoor Use Only
Pollution Degree
2
*Operating outside the operating limits may damage the unit.
2.4.2 Weight and Dimensions
Net Weight
5.7 lb. (Chopper Head assembly included)
Controller
Dimensions
4.0 in x 8.5 in x 11.0 in
(H x W x L)

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3 Using the Chopper
3.1 How the Model 3502 Optical Chopper Works
The Model 3502 Optical Chopper is designed to interrupt light paths in optical
experiments at frequencies from 4 Hz to 10.65 kHz. Both single- and dual-beam
experiments can be performed across a broad range of chopping frequencies. The
Chopper has a crystal-controlled frequency synthesizer that serves as an internal
reference frequency for locking the Chopper to a particular chopping frequency.
Reference frequencies can also be provided through the Sync In BNC connection
to allow the Chopper to lock to an external source.
Several measures ensure that jitter and drift of the chopping frequency is reduced
to a minimum. Precision photo-etched wheels are mounted on a high quality DC
motor. The Model 3502 Optical Chopper Head has a photo-sensor for monitoring
the chopping frequency of the outer part of the wheel. The Chopper Controller
then actively stabilizes the motor speed to match the desired chopping frequency.
This technique minimizes phase noise at the chopping frequency and provides for
long-term stable chopping with minimal frequency drift.
Figure 8 shows a block diagram of the Model 3502 Optical Chopper system.
Programmable divide/multiply circuitry allows for harmonic or subharmonic
locking of the Chopper to the reference frequency. In addition, the phase of the
chopping frequency may be varied over a -180 to +179 degree range with respect
to the reference frequency. A variety of TTL-level outputs are available for use in
triggering lock-in amplifiers, oscilloscopes, photon counters, or boxcar averagers.
The chopping frequency, as well as a number of other operating parameters, can
be viewed on the front panel display. Easy-to-use cursor keys provide easy
adjustment of operating parameters. From the front panel the user can store and
recall up to nine instrument setups. A USB 2.0 interface provides remote
operation of all instrument functions.
The Chopper Head can be mounted on a 1/2”-diameter post or bolted directly to
a standard optical bench. The Model 3502 Optical Chopper is supplied with six
Chopper wheels and a wheel cover. The Model 3502-BASE Optical Chopper does
not include any chopper wheels, and must be ordered separately.

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3.2 Mounting the Unit
3.2.1 Chopper Head
The Model 3502 Optical Chopper Head (Figure 9 and Figure 10) may be secured
to standard optical benches using ¼”-20 or M6 bolts. The bolts pass through the
mounting plate perpendicular to the plane of the optical bench. This mounting
method provides the advantage of allowing the wheel to be rotated by loosening
the ¼”-20 set screws on the side of the motor mount. Do not over-tighten the set
screws.
The Model 3502 Optical Chopper head may also be mounted on standard ½”
optical bench rods. First, loosen the two ¼”-20 set screws. (These secure the head
to the mounting plate by compressing on the dowel.) Remove the dowel and
mounting plate assembly. Insert the ¼”-20 knob (supplied with the Chopper) into
the base of the head. This knob is inserted into the same hole occupied by the
dowel. Slide the motor mount onto the ½” optical bench rod and hand- tighten the
knob. Do not over-tighten.
Figure 8: Functional block diagram for Model 3502 Optical Chopper.

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Figure 9: Model 3502 Optical Chopper Head with wheel cover installed.

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Figure 10: Dimensions of Model 3502 Optical Chopper Head. Dimensions in inches (mm).
3.2.2 Chopper Motor
The operating life of the Chopper motor is limited. Long-term use of the motor at
high speed will result in faster wear and a shorter lifetime. Contact Newport for
details about the replacement part, 3502-MOTOR, if this becomes necessary.
3.2.3 Mounting a Wheel
Six wheels are shipped with Model 3502 Optical Chopper, shown in Figure 11
below (these wheels are not included in the Model 3502-BASE, and must be
ordered separately). To install or change a wheel first power off the Chopper
Controller. Secure the chopping head to a work surface. Remove the four 4-40
screws that secure the retaining cap over the wheel, while taking care not to bend
the wheel on the optical pickup. Install the replacement wheel, retaining cap, and
4-40 screws. Do not over-tighten the screws. Please note that if a wheel is bent
during the installation/removal process, it can be very difficult to straighten again.
This may degrade the stability of operation of the Model 3502 Optical Chopper
system, and a replacement wheel may be required.

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Figure 11: Chopper wheels. Top row: 2-slot and 60/2-slot wheels. Middle row:7/5-slot and 42/30-slot wheels.
Bottom row: 60-slot and 100-slot wheels. All wheels are 4.50” (114.3 mm) O.D.

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WARNING
The moving wheel may inflict injury. The operator should ensure the
safety of personnel who may be exposed to this hazard.
3.2.4 Mounting the Wheel Cover
WARNING
The wheel cover is provided for safety and its installation is
encouraged. The Chopper wheel can cause injury if it is touched while
rotating. This is especially critical if you find yourself reaching into your
optical set-up with the lights off. You may want to use the Chopper
wheel cover to reduce the chance of injury.
The wheel cover attaches to the Chopper Head with four screws. The wheel cover
is made of 0.031” (0.80 mm) aluminum with an anti-reflective black anodized
coating. Two concentric slots, etched in both faces of the cover, allow apertures
of various sizes according to the table below. The wheel cover dimensions are 5”
x 5” x 0.5”.
Wheel Type
Model Number
Largest Beam Diameter
Inner Cover Slot
Outer Cover Slot
2-slot
3511
0.295” (7.50 mm)
0.394” (10.00 mm)
7/5-slot
3512
0.295” (7.50 mm)
0.394” (10.00 mm)
42/30-slot
3513
0.135” (3.44 mm)
0.138” (3.51 mm)
60-slot
3514
-
0.107” (2.71 mm)
100-slot
3515
-
0.064” (1.62 mm)
60/2-slot
3516
0.295” (7.50 mm)
0.107” (2.71 mm)
The wheel cover is also provided to reduce the generation of stray light that could
interfere with your measurements. The Chopper head uses an IR sensor to detect
Chopper wheel motion. The source in this sensor emits light of approximate
wavelength 950 nm. The wheel cover will greatly reduce the amount of sensor-
radiated stray IR light picked up by your experiment detector.
To install the wheel cover, first install a wheel on the Chopper hub. Then, slide
the wheel cover over the wheel. Please note that it can require some force to
separate the wheel cover’s mounting flanges far enough to fit over the motor
housing. Once the mounting flanges are lowered past the motor, align one of the
four flange holes with a threaded hole in the motor base and loosely attach the

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cover to the base with one of the 4-40 x 3/8” mounting screws. Loosely fasten the
three remaining screws. Tighten the four screws after they are installed.
3.3 Initial Setup
WARNING
The Model 3502 Optical Chopper Controller is intended for use ONLY
with Newport Model 3502 Optical Chopper motor heads. Connection of
other devices to the unit’s motor connectors may cause damage to the
unit or the connected device, fire, and/or personal injury.
WARNING
Before operating the Model 3502 Optical Chopper Controller, thoroughly
read and understand this User’s Manual!
This section contains information on how to connect Model 3502 Optical Chopper
Controller to your local mains power and how to connect the Chopper Head to the
Chopper Controller.
3.3.1 Power
Make sure that that power switch is in the OFF position. Connect the male end of
the provided AC power cable to the mains supply. Connect the female end to the
three-pronged input receptacle on the back of the Chopper Controller.
WARNING
To avoid electric shock, connect the instrument to building earth-ground,
3-prong receptacles by using the supplied power cord only. Failure to
observe this precaution can result in damage to the product, fire, severe
injury, or death.
WARNING
Do not position this product in such a manner that would make it difficult
to disconnect the power cord.
WARNING
Position the equipment so that access to the mains ON/OFF switch is
readily available. In the event of a hazard, press the grey Power switch on
the lower right of the front panel to the OFF position to turn power OFF
to the internal electronics and fully disconnect the power cord of the
Controller from mains power.