THORLABS MC2000 User manual

MC2000, MC2000-EC
Optical Chopper
Operating Manual

Optical Chopper System
18488-D02 Rev G, September 24, 2012 Page 2 www.thorlabs.com
Table of Contents
ePart 1.Safety Warnings...........................................................................................................................5
Part 2.Product Overview.........................................................................................................................6
Front Panel Description .............................................................................................................................................7
Rear Panel Description ..............................................................................................................................................7
Part 3.Setup.............................................................................................................................................8
Part 4.Basic Operation............................................................................................................................9
4.1.Internal Reference Operating Mode ......................................................................................................9
4.2.External Reference Mode........................................................................................................................9
4.3.Reference-Out Signal.............................................................................................................................10
Part 5.Advanced Operating Instructions..............................................................................................11
5.1.Internal Frequency Synthesizer............................................................................................................11
Setup for Internal Reference Frequency ..................................................................................................................11
Selecting the REFERENCE OUT signal .................................................................................................................11
5.2.External Reference Mode......................................................................................................................11
Setup for External Reference Frequency .................................................................................................................11
Selecting the REFERENCE OUT signal .................................................................................................................11
5.3.Harmonic Reference Generation..........................................................................................................12
Setup for External Reference Frequency .................................................................................................................12
Setting the Reference Harmonic..............................................................................................................................12
Setting the Sub-Harmonic........................................................................................................................................12
Combining the Harmonic and Sub-Harmonic Modes..............................................................................................12
Selecting the REFERENCE OUT signal .................................................................................................................12
5.4.Two-Frequency Chopping.....................................................................................................................12
Selecting the REFERENCE OUT signal .................................................................................................................12
Setting the Chopping Speed in the Two Frequency Mode.......................................................................................13
5.5.Two-Slot Blade .......................................................................................................................................13
Setup for Two-Slot Blade Reference Frequency......................................................................................................13
Selecting the REFERENCE OUT signal .................................................................................................................14
Part 6.Remote Communications...........................................................................................................15
6.1.Installing the USB Drivers.....................................................................................................................15
6.2.Command Line Interface ......................................................................................................................15
6.3.Commands..............................................................................................................................................16
6.4.Blade Indexes..........................................................................................................................................18
Part 7.Maintenance and Troubleshooting...........................................................................................19
7.1.Cleaning ..................................................................................................................................................19
7.2.Diagnostic Messages...............................................................................................................................19
Part 8.Fuse Replacement and Line Voltage Selection ........................................................................20
8.1.Materials Needed....................................................................................................................................20
8.2.Fuse Replacement and Line Voltage Selection....................................................................................20

Optical Chopper System
18488-D02 Rev G, September 24, 2012 Page 3 www.thorlabs.com
Part 9.Visual Menu Structure...............................................................................................................22
Part 10.Specifications .............................................................................................................................23
Part 11.Drawings.....................................................................................................................................26
Part 12.Regulatory ..................................................................................................................................28
12.1.Waste Treatment is Your Own Responsibility....................................................................................28
12.2.Ecological Background..........................................................................................................................28
Part 13.Certificate of Conformity...........................................................................................................29
Part 14.Thorlabs Worldwide Contacts ...................................................................................................31

Optical Chopper System
18488-D02 Rev G, September 24, 2012 Page 4 www.thorlabs.com
Table of Figures
Figure 1:Front Panel............................................................................................................................. 7
Figure 2:Rear Panel.............................................................................................................................. 7
Figure 3:Circuit Board Layout with 110/220 VAC Switch................................................................ 21
Figure 4:Console Dimensional Drawing............................................................................................ 26
Figure 5:Chopper Head Dimensional Drawing.................................................................................. 27

Optical Chopper System
18488-D02 Rev G, September 24, 2012 Page 5 www.thorlabs.com
Part 1. Safety Warnings
Warning Electrical Shock
To avoid electrical shock the power cord protective grounding conductor must be
connected to ground. Refer servicing to qualified personnel.
The unit must be powered off, unplugged from the AC input power source,
and disconnected from all external devices before removing the cover and
replacing the fuse. Failure to do so may cause serious injury to the user since high
voltages exist within the unit.
Thorlabs provides the proper 120 VAC power input cable with each MC2000 for use in the United
States and the appropriate 230 VAC input cable with each MC2000-EC for use in Europe. If using this
unit anywhere else, the user will need to supply a properly grounded power cable to power the unit. If
something should go wrong with the unit, do not attempt to fix. Call a Thorlabs representative and
arrange for repair. The unit should never be opened unless changing the fuse or line voltage as described
in Section 5.
Thorlabs ships all units configured to operate in the United States (i.e. line voltage 115 VAC, 60 Hz and
250 mA fuse installed). It may be necessary to change the line voltage to 230 VAC and replace the fuse
with a 125 mA Slow Blo fuse. Care must be taken when configuring the unit. See Section 5 for complete
details.
Warning Rotating Blade!
Keep hands clear while the blade is spinning. Turn power off before servicing.

Optical Chopper System
18488-D02 Rev G, September 24, 2012 Page 6 www.thorlabs.com
Part 2. Product Overview
The MC2000 Optical Chopper is a precision instrument utilizing advanced features to meet the most
demanding applications. The MC2000 uses a phased-locked loop (PLL) motor speed control design to
precisely maintain the chopping speed and phase to a reference signal. An internal, crystal-stabilized,
frequency synthesizer provides an accurate and stable reference frequency for long-term stable
performance.
Unlike conventional, open-loop speed control designs, the PLL speed control circuit also allows the
MC2000 chopper to be synchronized to external reference signals, including other MC2000 choppers
and reference sources such as DSP lock-in amplifiers.
For more advanced measurements, the MC2000 can lock to a harmonic, sub-harmonic, or fractional-
harmonic of an external reference frequency. The on board microprocessor is used to multiply the
external reference up to the 15th harmonic or to divide the reference down to the 15th sub-harmonic. By
combining both the frequency multiplication and division together, a fractional harmonic can be
obtained.
The MC2000 also supports 2-frequency chopping from a single chopper blade. A special blade is
available with 7 outer slots and 5 inner slots. This slot combination allows a single beam to be split and
individually modulated for ratio metric experiments. Another example application is a pump-probe
experiment where the pump beam is modulated at the outer frequency while modulating a probe beam at
the inner frequency. The MC2000 provides the sum and difference frequencies of the 2-frequency blade
for accurate lock-in detection of the frequency-mixed response.
A high quality, rare earth magnet, DC motor and a photo-etched optical chopper wheel are the top two
design elements responsible for this device’s high precision. The compact optical head has a wide base
for extra stability. The base is slotted for two 1/4"-20 mounting screws on 3" centers. The interface cable
uses circular snap-on connectors for easy setup.
The MC2000 controller includes a 240 x 128 pixel graphics display for
setting and monitoring chopper functionality. All of the functions are
accessible through a front panel control knob with turn and push control.
Multiple user setups can be easily saved and recalled from non-volatile
memory. A USB interface is included as a standard feature for remote
PC control of the MC2000.
Thorlabs offers a number of different blades to extend the range of the
chopping frequency. A standard 10-slot blade is included with the
MC2000. 2-slot, 15-slot, 30-slot, 60-slot, and 2-frequency blades are
also available.

Optical Chopper System
18488-D02 Rev G, September 24, 2012 Page 7 www.thorlabs.com
Front Panel Description
Figure 1: Front Panel
Rear Panel Description
Figure 2: Rear Panel
Control Knob
This knob is used to highlight and select menu items.
LCD Display
The controller menus are displaye
d
h
e
r
e.
Power
Press to toggle
p
owe
r
Ext Input
The external reference signal is connected to this
input BNC (TTL / CMOS logic level).
Ref Output
The reference
output signal
selected by the
reference out menu
(CMOS logic
level
)
.
Cooling Fan
Do not block when the
unit is operating.
Modular Interface
Connector for the
optical hea
d
AC input receptacle
Requires an IEC compatible
plug with ground terminal.
Cord supplied for US
o
p
eration.
Fuse Holder
The system fuse is
installed here.
USB 2.0 Por
t

Optical Chopper System
18488-D02 Rev G, September 24, 2012 Page 8 www.thorlabs.com
Part 3. Setup
1. Carefully unpack the MC2000 controller, optical head, and accessories. See below for a
complete list of parts. If any of the items appear damaged or missing, do not use the MC2000.
Call Thorlabs, or email [email protected]om and arrange for a replacement.
Parts List:
•MC2000 Control Box
•MC2000 Optical Chopping Head
•MC1F10: 10-slot chopping blade
•2 meter mini circular cable for optical head / control box interface
•This Operating Manual
•Power Supply Line Cord: 120 VAC with the MC2000 or 230 VAC with the MC2000-EC
•125 mA Fuse for use at 230 VAC operation (250 mA fuse installed in unit)
•1/16" Allen Key for blade replacement
•0.05" Allen Key for hub alignment.
•(3X) 4-40 x 1/8" Phillips Pan Head Screws with Internal Tooth Washers
2. Remove the 3 mounting screws and lock washers from the chopper blade hub using the 1/16"
hex key provided.
3. Unpack the 10-slot blade and install onto chopper blade hub using the 3 screws and washers
removed in the previous step. Tighten the screws securely with the hex wrench.
4. Attach the modular cord into the circular connector labeled ‘OPTICAL HEAD’ on the back of
the MC2000 controller and plug the other end into the circular connector on the optical head.
5. Mount the optical head on a sturdy surface in an area free of obstructions. Make sure the blade
can spin freely.
6. Attach the AC line cord to the MC2000 and plug into an AC outlet.
Note: the MC2000 can be operated from 100/115 VAC or 230 VAC. A voltage selector switch is located
inside of the MC2000 controller. If you are not sure what operating voltage your unit is set to, proceed
immediately to Part 8. Fuse Replacement and Line Voltage Selection on page 20 for instructions on
setting the operating voltage.

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Part 4. Basic Operation
4.1. Internal Reference Operating Mode
The MC2000 is most often used in the internal reference mode where the chopping speed is set
internally.
1. Turn the MC2000 power on. The LCD display will show the Thorlabs logo and firmware
revision number before changing to the top-level menu list. The display will then show the
current menu, menu options, and operating status of the unit. By turning the front panel control
knob, different menu items can be highlighted. Push the control knob to select the highlighted
item.
2. Set the MC2000 parameters to the following for quick internal operation:
•Blade – (MC1F10)
•Ref. In – (INTERNAL)
•Freq. – Set to the desired frequency
•Phase – Set to the desired phase
•Harm N – Set the N harmonic to 1
•Harm D – Set the D harmonic to 1
3. Highlight and select Run Mode. The unit will adjust its speed and lock onto the set speed within
a few seconds.
Note that all menu parameters can be changed in standby mode, while only frequency, phase and N/D
harmonic parameters can be changed in run mode. The unit always powers up in standby mode.
4.2. External Reference Mode
This mode allows the user to control the chopper blade with a logic-level external reference signal.
1. To enable external reference mode, attach a TTL or CMOS logic level reference signal to the
‘EXT REF INPUT’ BNC on the front panel. Turn the MC2000 power on.
2. Set the MC2000 parameters to the following for quick external operation:
•Blade – (MC1F10)
•Ref. In – (EXTERNAL)
•Freq. – Set to the desired frequency
•Phase – Set to the desired phase
•Harm N – Set the N harmonic to 1
•Harm D – Set the D harmonic to 1

Optical Chopper System
18488-D02 Rev G, September 24, 2012 Page 10 www.thorlabs.com
3. Highlight and select Run Mode. The unit will adjust its speed and lock onto the external
reference speed within a few seconds.
4.3. Reference-Out Signal
The MC2000 supports a number of different reference out signals. For reference output selection,
highlight and select the external reference out signal from the following menu list. This list is described
in more detail in the following sections.
•TARGET – The reference out signal synthesized internally from a unit’s crystal clock
•ACTUAL – The reference out signal obtained from the feedback sensor reading the outer slots
on a chopper wheel
•INNER – Reference out signal obtained from the feedback sensors reading the inner slots of a
two slotted chopper wheel. (Note: This menu item is only displayed when a two-slot blade is
selected.)
•OUTER – Reference out signal obtained from the feedback sensor reading the outer slots of a
two slotted chopper wheel. (Note: This menu item is only displayed when a two slot blade is
selected.)
•SUM – The reference out signal obtained from the two frequency blade 5/7 sum
•DIFF – The reference out signal obtained from the two frequency blade 5/7 difference

Optical Chopper System
18488-D02 Rev G, September 24, 2012 Page 11 www.thorlabs.com
Part 5. Advanced Operating Instructions
5.1. Internal Frequency Synthesizer
The MC2000 is most frequently used in this mode where the chopper wheel frequency is locked to an
internal crystal stabilized frequency reference. The PLL motor speed control circuit maintains a precise
lock to the frequency and phase of the internal reference frequency creating an ultra-stable chopping
signal. The chopper wheel phase can be continuously adjusted.
Setup for Internal Reference Frequency
Follow the setup procedures for internal reference operating mode in Part 4: Basic Operation on page 9.
Selecting the REFERENCE OUT signal
In the internal frequency mode, the reference output signal can be set to the actual chopper wheel
frequency (ACTUAL) or the internal frequency synthesizer (TARGET). In most cases, such as when
selecting a reference for a lock-in amplifier, the chopper wheel frequency will be used since it provides a
direct measurement of the chopper phase and frequency. The chopper wheel reference is derived from
two photo-interrupters on the optical head that sense the motion of the chopper blade.
The internal frequency synthesizer has slightly less phase jitter than the chopper wheel reference since it
is not affected by external disturbances. Therefore, there may be cases where using the internal
synthesizer as the reference output yields better performance (i.e. when synchronizing multiple
choppers).
5.2. External Reference Mode
A major benefit of using a PLL circuit to control the chopper wheel speed is the chopper can be locked
precisely to an external reference signal. This allows the MC2000 to be used in advanced setups, for
example, multiple MC2000 choppers can be synchronized to a single reference signal, or master-slave
combinations where one chopper is the master reference and a second chopper is slaved off the reference
output of the first. The latter example provides a convenient way to measure long decay time
fluorescence and other similar types of experiments.
The MC2000 will accept a TTL or CMOS logic level input as an external reference. The advanced PLL
design used in the MC2000 even accepts reference signals that do not have a 50% duty cycle. A special
feature of the external reference mode, locking to harmonics and sub-harmonics of the reference signal,
is described in the following section.
Setup for External Reference Frequency
Follow the setup procedures for external operating mode in Part 4: Basic Operation on page 9.
Selecting the REFERENCE OUT signal
In the External frequency mode, the reference output signal (ACTUAL) can be set to the actual chopper
wheel frequency or the internal frequency synthesizer (TARGET). Most cases in this mode, only the
actual chopper wheel frequency will ever be used.

Optical Chopper System
18488-D02 Rev G, September 24, 2012 Page 12 www.thorlabs.com
5.3. Harmonic Reference Generation
Harmonic generation is a special feature available when operating in the external reference mode. The
on board microprocessor is used to multiply the external reference up to the 15th harmonic or to divide
the reference down to the 15th sub-harmonic. By combining both the frequency multiplication and
division together, a fractional harmonic can be obtained. The new frequency is used as the chopper
reference for chopping at a variety of frequency combinations, all derived from the external reference.
Setup for External Reference Frequency
Follow the setup procedures for external operating mode in Part 4: Basic Operation on page 9.
Setting the Reference Harmonic
Highlight and select the reference harmonic N menu item and enter a scroll bar value between 1 and 15.
Setting the Sub-Harmonic
Highlight and select the reference harmonic D menu item and enter a scroll bar value between 1 and 15.
Combining the Harmonic and Sub-Harmonic Modes
The sub-harmonic divider follows the harmonic multiplier. Therefore, the generated reference frequency
will always be
D
N
ff REFEXT =. (eq. 1)
There are no special steps to combine these two features since they are always active.
Selecting the REFERENCE OUT signal
In the Harmonic frequency mode, a fractional harmonic reference output signal
D
N
ACTUAL)(,
or the internal frequency synthesizer (TARGET) can be selected. Most cases in this mode, only the
(ACTUAL) fractional harmonic reference output signal will ever be used.
5.4. Two-Frequency Chopping
A special two-frequency blade is available from Thorlabs, which has seven slots on the outer portion of
the wheel and five slots on the inner part of the wheel. This unique prime number combination allows
the same chopper to discriminately chop two different light paths. This can be used in ratio metric
measurements and pump-probe type experiments.
Selecting the REFERENCE OUT signal
The MC2000 provides two additional reference outputs in this mode. The sum (SUM), and the
difference (DIFF) reference frequencies track the combined signal paths when they are frequency mixed
together. The example below illustrates this:

Optical Chopper System
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For example, the MC2000 is set to run the outer blade set at 70 Hz. The inner blade, by virtue of the
ratio of inner to outer slots will be running at 50 Hz. If a light path is common to both the inner and
outer blades, the signal will see a sum frequency of 120 Hz and a difference frequency of 20 Hz.
Setting the Chopping Speed in the Two Frequency Mode
The chopping frequency for the two-frequency blade is set the same way as described above for the
single frequency blades.
Note: The MC2000 synchronizes the outer portion of the two-frequency blade to the internal synthesizer
or external reference. The inner portion is chopping at a rate given by, 5/7 * reference
7
5
REFInner ff =, (eq. 2)
For example, if the internal reference (or external reference) frequency is 100 Hz, the outer portion of
the blade would be chopping at 100 Hz and the frequency of the inner portion could be found using
equation 2,
HzHzfInner 42.71
7
5
100 == .
5.5. Two-Slot Blade
The 2-slot blade provides very stable low frequency chopping up to a frequency of 99 Hz. To
accomplish the high stability required, an outer blade frequency with a 50:1 ratio is used to minimize the
jitter. The optical chopper uses this outer frequency to lock the blade to either the internal or external
frequency generator. In applications where phase is important, the MC2000 uses a dual photo-interrupter
arrangement on the head to track the phase of the inner slot.
Setup for Two-Slot Blade Reference Frequency
Follow the setup procedures for external operating mode in Part 4: Basic Operation on page 9.

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18488-D02 Rev G, September 24, 2012 Page 14 www.thorlabs.com
Selecting the REFERENCE OUT signal
If operated as a stand-alone unit, the external reference out signal will most likely be set to the inner
(INNER) mode. This will set the external reference out and display information to the inner slot
frequency and phase of the blade.
If two units are to be synchronized in a master-slave configuration, the master unit will act as the
frequency generator for the slave by connecting the reference out (REF OUT) of the master to reference
in (REF IN) of the slave.
Master:
•Blade – (MC1F2)
•Ref. In – (INTERNAL)
•Ref. Out – (OUTER)
•Freq. – Set to the desired frequency.
•Phase – Set to the desired phase.
Slave:
•Blade – (MC1F2)
•Ref. In – (EXTERNAL)
•Ref. Out – (INNER)
•Freq. – Set to the desired frequency.
•Phase – Set to the desired phase.

Optical Chopper System
18488-D02 Rev G, September 24, 2012 Page 15 www.thorlabs.com
Part 6. Remote Communications
The MC2000 may also be controlled by a command line language through the USB port. This is offered
to enable operation through a terminal interface or for those who may want to write their own program
to control the system.
6.1. Installing the USB Drivers
Prior to running the command line interface, the USB drivers must be installed. The MC2000 must not
be connected to the PC while installing the drivers. Insert the CD that was supplied with your unit into
your PC. From the dialog box that is displayed, select the Install Drivers button. If the dialog box is not
displayed, browse to the CD and run CD-Starter.exe. Follow the onscreen prompts to install the driver.
After the driver is installed, attach the MC2000 to the PC and power it on. Your PC will then detect the
new hardware and will prompt you when the installation is complete.
6.2. Command Line Interface
Once the USB drivers have been installed and the unit connected to the PC and powered on, configure
the terminal emulator as follows:
•Baud Rate = 115.2K Bits Per Second
•Data Bits = 8
•Parity = None
•Stop Bits = 1
•Flow Control = None
If the connection is correct you will see the following after pressing the “Enter” key.
Command error CMD_NOT_DEFINED
Followed immediately by the prompt:
>
The basic structure of the interface is a keyword followed by either an equals sign “=” or a question
mark “?”. The “=” or “?” will determine if the string is a command or a query. All strings (commands
and queries) must be terminated by a carriage return (CR) or pressing the ENTER key on the computer.
The command structure is as follows:
Keyword=argument(CR)
Where “keyword” defines the function and “argument” is a numerical value followed by a carriage
return (CR). See listing below.

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The query structure is as follows:
Keyword?(CR)
The “keyword” defines the function and the question mark (?) indicates a query. The string is terminated
with a carriage return (CR). See listing below. There are a few exceptions to this which are noted below.
The prompt symbol “>” will appear on power up and after a command is accepted by the system
indicating it is ready to receive another command line.
6.3. Commands
The following list shows all of the available commands and queries, and summarizes their functions:

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Command Syntax* Description
Get Commands ? List the available commands.
Get Identification id? Returns the model number and firmware version.
Set Frequency freq=nSet the desired internal reference frequency.
Get Frequency freq? Returns the internal reference frequency.
Set Blade Type blade=nSet the blade type (nis number indicated in section 6.4).
Get Blade Type blade? Return the blade type (see section 6.4 for more details).
Set Harmonic Multiplier nharmonic=nSet Harmonic Multiplier applied to external reference frequency (1-15).
Get Harmonic Multiplier nharmonic? Returns the Harmonic Multiplier.
Set Harmonic Divider dharmonic=nSet the Harmonic Divider applied to external reference frequency (1-15).
Get Harmonic Divider dharmonic? Returns the Harmonic Divider.
Set Phase phase=nSet the Phase adjust (0-360°).
Get Phase phase? Returns the Phase adjust.
Set Enable enable=nSet Enable (0=disabled, 1=enabled).
Get Enable enable? Get Enable.
Set Reference ref=nSet the reference mode (0=internal, 1=external).
Get Reference ref? Returns the reference mode.
Set Ref Output output=nSet the output reference mode (0=target, 1=actual).
Get Ref Output output? Returns the output reference mode.
Set Display Intensity intensity=nSet the Display Intensity (1-10).
Get Display Intensity intensity? Returns the Display Intensity.
Get Reference Frequency input? Returns the current supplied external reference frequency.
Restore restore Restore the factory default parameters.
Get Verbose verbose? Returns the verbose mode.
Set Verbose verbose=n When verbose mode is set to 1, status messages are output on the USB.
Set Language text=nn= 0 sets text to English, n= 1 sets text to Chinese.
* All commands and queries are in lower case letters.
If the keyword, format, or argument is incorrect or out of range, the unit will return an error string. The
function is determined by the value set with the mode command in the above table.

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6.4. Blade Indexes
Blade type can be gotten or set through the command line interface using the commands “blade?” and
“blade=n”, respectively. These commands do not denote blade type using product names. Rather, they
index blade type using the numbers from 0 to 7. The following table provides the mapping:
Blade Index
MC1F2 0
MC1F6 1
MC1F10 2
MC1F15 3
MC1F30 4
MC1F60 5
MC1F100 6
MC1F57 7

Optical Chopper System
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Part 7. Maintenance and Troubleshooting
7.1. Cleaning
The MC2000 should only be cleaned with a soft cloth and mild soap detergent or isopropyl alcohol. Do
not use a solvent-based cleaner.
The optical chopper wheel may build up a layer of dust over time on the leading edges of the wheel. To
clean the wheel, remove it from the optical head and wipe it clean with a cloth dampened in isopropyl
alcohol. To help prevent the chopper wheel from rusting in high humidity environments, wipe the blade
with a clean rag sprayed with a light lubricating rust inhibitor (e.g. WD40 or similar).
7.2. Diagnostic Messages
When the MC2000 senses a problem with the chopper operation, it will display various messages to help
identify the source of the problem.
•Freq. Not Locked This indicates that the chopper speed could not lock to the set frequency or the
external reference. If this occurs, check the unit has been set to the correct
blade (as indicated on power up). If this problem persists, contact Thorlabs for
assistance.
•Phase Not Locked This indicates that the chopper phase could not lock to the set phase setting. If
this problem persists, contact Thorlabs for assistance.
•No Int. Reference This message is displayed when the unit is set to external reference but it does
not detect an external reference input. Check that your external reference
source is connected to the BNC labeled EXT REF IN.

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Part 8. Fuse Replacement and Line Voltage Selection
Thorlabs ships the MC2000 unit configured to operate at 100/115 VAC. The line voltage and installed
fuse must be changed to operate this unit at 230 VAC. Follow the instructions below to change the line
voltage if necessary.
Warning Electrical Shock
The unit must be powered off, unplugged from the AC input power source,
and disconnected from all external devices before removing the cover and
replacing the fuse. Failure to do so may cause serious injury to the user since high
voltages exist within the unit.
8.1. Materials Needed
•MC2000 Operating Manual
•250 mA Type IEC60127-2/III, Type ‘T’ Slo-blo Fuse – The 250 mA fuse is installed from the
factory and must be installed when operating the unit at 100/115 VAC.
•125 mA Type IEC60127-2/III, Type ‘T’ Slo-blo Fuse – Thorlabs supplies a 125 mA fuse to be
installed when operating at 230 VAC.
•Phillips Head Screwdriver (#2 Preferred) – Motorized screwdrivers are not recommend.
8.2. Fuse Replacement and Line Voltage Selection
1. Important! – Make sure the power cord, optical head, and any external devices are disconnected
before continuing. See warning above.
2. Remove the two screws securing the enclosure cover with a Phillips head screwdriver. The
screws are located on the bottom side, rear corners of the unit. Place the screws in a safe
location.
3. Carefully remove the cover by sliding it toward the rear of the unit.
4. To change the line voltage, locate the line select switch behind the power switch. Select the
appropriate line voltage by adjusting the switch to either 110 or 220. Select 110 if operating at
100 to 120 VAC. Select 220 for operation from 220 to 240 VAC.
5. Replace the enclosure cover and secure with the enclosure screws.
6. Locate the fuse holder below the power input connector. Slide the fuse tray out using a flat head
screwdriver. Remove the fuse and replace with the appropriate value as described below:
•100 – 120 VAC operation – Use the 250 mA fuse
•220 – 240 VAC operation – Use the 125 mA fuse