Alphasense OPC-R1 User manual

072-0500 Alphasense User Manual
OPC-R1 Optical Particle Counter Issue 1
Alphasense Ltd Page 1 of 33 February 2019
Sensor Technology House, 300 Avenue West, Skyline 120, Great Notley. Essex.CM77 7AA. UK
Tel: [phone] - Fax: [phone]
Email: [e-mail] - Web: www.alphasense.com
Contents
1 Quick Start
2 Product Specification
3 Health and Safety and Regulatory Information
4 How the OPC-R1 works
5 PM Measurement
6 Sampling the environment
Connecting and running the OPC
7 Connecting Power and Taking Readings
8 Running the OPC-R1 using the Alphasense software
·Installation
·Data Display and taking measurements
·Other software functions
9 Running the OPC-R1 using direct API control
10 Revision Control
11 Appendices
A. FAQs
B. Installing the device driver
Windows XP
Windows 7
Windows 8, 8.1 and 10
C. Updating Firmware
D. Summary of firmware commands
E. Checksum

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Tel: [phone] - Fax: [phone]
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1 Quick Start
The purpose of this manual is to explain how to set up, install and use the Alphasense Optical
Particle Counter OPC-R1 for measuring PM1, PM2.5 and PM10, as well as measuring particle size
distributions in real time. Note it is also possible to set the unit up to measure PM4.25.
When using this OPC for the first time we recommend that you use the Alphasense SPI adapter.
This will enable you to very quickly use the OPC at your desk by running it off a Windows PC or
laptop using the Alphasense software. Apple and Unix compatible software are not available.
Initially a full deployment package will have been provided with the OPC-R1. In the future this will
be available via the web site or through contact with Alphasense.
Full instructions for carrying out the installation, (specifically a driver must be installed for the SPI
adapter) and for the use of the software are in Appendix B and section 9. Please note the driver
and the SPI adapter are the same as that used for the OPC-N2 and N3.
You can view the data options along with the data resolution and range when the OPC-R1 is
connected to a PC running the Alphasense-supplied software. Please note that is not the same
software that runs the OPC-N2 or the OPC-N3. This also provides a useful reference to those
customers who wish to develop their own software.
The OPC-R1, unlike the OPC-N2 and N3, does not have a standalone mode where the data is
stored directly on an onboard SD card.
Temperature and humidity sensors are fitted as standard on the OPC-R1. Temperature and
humidity compensation is not currently carried out but this will be offered in the future.

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2 OPC-R1 Specification
All dimensions in millimetres (± 0.15 mm)
MEASUREMENT
Particle range (
m
m) Spherical equivalent size (based on
RI of 1.5+i0) 0.35 to 12.4
Size categorisation (standard) Number of software bins 16
Sampling interval (seconds) Histogram period (recommended) 1 to 30
Sample flow rate mL/ min 240
Max particle count rate Particles/ second 10,000
Detection limits (PM10) Minimum
Maximum (electronic limit) 0.01 mg/m3
1 500 mg/m3
Coincidence probability % at 10
6
particles/ L 0.7
POWER
Measurement mode mA 95-100
Non-measurement mode mA Laser and fan off 5
Transient power on start-up mW for 1 ms <5000
Voltage range V DC 4.8 to 5.2
KEY SPECIFICATIONS
Digital Interface SPI (Mode 1)
Laser classification as enclosed housing Class 1
Temperature range °C -10 to 50
Humidity range % rh (continuous) 0 to 95 (non-condensing)
Weight g < 30
Table 1. Power and environmental performance limits

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3 Health and Safety
The OPC-R1 uses an embedded diode laser operating at 4-8 mW (max. 11 mW) at a wavelength of
639 nm. The OPC-R1 is a Class 1 laser product, since the user does not have access to the laser
source. The OPC-R1 is designed for OEM use, normally mounted in a secondary housing. The
user must not open or adjust any parts of the OPC-R1. It is the user’s responsibility to ensure that
the unit is used safely and complies with any local regulations. Do not remove any safety stickers
or warnings.
DO NOT remove the external housing: this not only ensures the required airflow but also protects
the user from laser light. Removal of the casing may expose the user to Class 3B laser radiation.
You must avoid exposure to the laser beam. Do not use if the outer casing is damaged- return to
Alphasense. Removal of the external housing exposes the OPC circuitry which contains
components that are sensitive to damage by static discharge.
4 How it Works
Like conventional optical particle counters, the OPC-R1 measures the light scattered by individual
particles carried in a sample air stream through a laser beam. These measurements are used to
determine the particle size (related to the intensity of light scattered via a calibration based on Mie
scattering theory) and particle number concentration. Particle mass loadings- PM1, PM2.5 and PM10,
are then calculated from the particle size spectra and concentration data, assuming a particle
density and refractive index (RI). Default settings, weighting index 2 are: density 1.65 g/ml, RI
1.5+i0. Respiratory profiles are included in the PM calculations. It is also possible to select PM4.25
instead of one of the other PM values.
The OPC-R1 contains 10 weighting index sets, each comprising a weighting value for each of the
16 size bins. Index Set 0 can be adjusted by the end user; the other 9 are factory set (See later for
more information).
The OPC-R1 classifies each particle size, at rates up to ~10,000 particles per second, recording the
particle size to one of 16 “bins”covering the size range from 0.35 to 12.4 μm. Please note the
maximum particles per second and the maximum mass detectable are based on the potential
performance of the electronics and will be reduced in actual measurements. The resulting particle
size histograms can be evaluated with user-defined sampling times from 1 to 30 second duration.
Longer times in dirty environments with high particle concentrations can result in the bins “over
filling”. If longer periods are needed it is recommended to undertake the averaging of shorter
measurement periods. This histogram data is transmitted via an SPI interface to a host computer.
The OPC-R1 is designed to minimise particle deposition within the unit and thus allow for prolonged
unattended operation in dusty environments. We would recommend the use of the OPC-N3 in very
dusty environments.
Consistent with most commercial Optical Particle Counters (OPCs), all particles, regardless of
shape are assumed to be spherical and are therefore assigned a ‘spherical equivalent size’. This
size is related to the measurement of light scattered by the particle as defined by Mie theory, an
exact theory to predict scattering by spheres of known size and refractive index (RI). The OPC-R1

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is calibrated using Polystyrene Spherical Latex Particles (PSLs) of a known diameter and known RI.
Correction factors can be applied for errors resulting from particles of different density or refractive
index.
5 PM measurements
The particle size histogram data recorded by the OPC-R1 sensor can be used to calculate the mass
of airborne particles per unit volume of air, expressed as μg/m3.
The accepted international standard definitions of particle mass loadings in the air are PM2.5 and
PM10, PM1 is not yet an international standard. These definitions relate to the mass and size of
particles that would be inhaled by a typical adult.
The OPC-R1 calculates the respective PM values according to the method defined by European
Standard EN 481. Conversion from the ‘optical size’of each particle as recorded by the OPC-R1
and the mass of that particle requires knowledge of both particle density and its RI at the
wavelength of the illuminating laser beam, 639 nm. The OPC-R1 assumes an average RI value of
1.5 + i0. The OPC-R1 allows a different value to be set for each size bin to correct for particle
density variation with particle size. The OPC-R1 has 10 bin weighting indexes, one is adjustable by
the end user and 9 are factory set. Please note that not all of these indexes will be defined in early
released units.
The default setting for each size bin assumes a Particle Density value of 1.65 g/ml, bin weighting
index 2, a figure that equates to a typical value found in many environments. Bin weighting index 0
can be modified by the end user, default setting is currently 1 for all bins.
Where it is known that different size fractions in the ambient aerosol have different densities (for
example, the smallest carbon particles will have a higher density than larger aggregates of the same
particles); different Particle Density values may be set for different bins to achieve a more accurate
determination of PM. The other indexes will be preset with values adjusted for common ambient
environments and to ensure that the OPC-R1 matches better to standard reference instruments
when used in the field and to correct for some of the missing mass below the OPC detection limit.
Contact Alphasense on how to modify standard settings.
Note
·The EN 481 standard definition for PM10 extends to particle sizes beyond the upper
measurable size limit of the OPC-R1. In some cases, this can result in the reported PM10
value being underestimated.
6 Sampling the environment
The sample air flow rate through the unit is determined by both the fan speed and any obstruction
that affects the inlet or outflow of the OPC. Therefore tubing, valves, baffles or obstructions that will
restrict air flow into or out of the OPC should be avoided. Particle distributions can also be affected
by sharp turns and narrow sample pipes. The maximum pressure drop through the entire flow
system must be less than 40 Pa.
However, because fan speed can vary, the sample flow rate through the OPC may vary also. Such
variations are monitored and corrected dynamically by the OPC so that the particle concentrations
and derived PM values are unaffected by moderate flow variations (patent pending).
The OPC R1 unit will operate adequately on its own on the bench; however it will need to be placed
in a secondary housing for use in the field.
Alphasense recommends that the OPC-R1 inlet is exposed directly to the target sample volume and
that the fan exhausts into an unconstrained space. An exhaust extension is provided to facilitate
this. The OPC-R1 can be positioned in any orientation, but to mitigate the effects of wind direction
on sampling it is best for the inlet to be pointing upwards. When mounted pointing upwards care
should be taken to avoid very large droplets or soot and grit from entering the unit due to gravity.
We recommend an “umbrella”or mushroom to protect the inlet but that does not interfere with

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particle flow. Coarse gauze filters can also be used to prevent the ingress of large particles or
insects without interfering with the fine particles being measured. All electrical connections must be
protected from moisture and temperatures outside of the operational range.
The temperature and humidity sensor is mounted on the OPC-R1 PCB. The values reported may
not represent the actual ambient conditions.
Connecting and Operating The OPC R1
7 Connecting power and taking readings
The OPC-R1 is shipped pre-calibrated. There are no user serviceable parts. Power and data
communications are provided via the SPI socket. Firmware updates use the SPI connector.
Connection to the OPC-R1 for real-time data transfer can be made via the SPI direct to your own
circuit’s internal bus using your own or the SPI interface provided by Alphasense. The SPI interface
supplied by Alphasense requires a USB A-B lead to connect to the USB port of a computer, this
must be ordered separately. The green LED shows that power is supplied to the OPC-R1 and the
red LED flashes when the PC and OPC-R1 are communicating.
SPI Connection
The SPI socket is a Molex 'Pico Clasp' 6 way Housing, Part Number 501330-0600. Pins are
assigned in table 2.
Pin
Function
1 Vcc
2 SCK
3 SDO
4 SDI
5 /SS
6 GND
Table 2. SPI pin assignments
OPC power requirement
The OPC-R1 requires a 4.8 to 5.2 Volt DC supply with minimum electrical noise, (< 30mV pk-pk)
This is stepped down to a 3v3 supply (via the SPI-ISS adapter) for the SPI logic lines. Except for the
Slave-Select logic line, the SPI interface lines are 5V tolerant but we recommend to run all at 3v3.
The OPC-R1 requires 95-100 mA with a short one amp transient at switch-on, check that the current
limit is not exceeded if multiple units are operated from a shared power supply
It is recommended to allow 2 second for the OPC to respond to the first SPI command after power-
up and >0.6 s after a switch peripherals/fan on sequence.
Software interface configuration
The following interface rules will help you to make a reliable connection with the OPC.
1. Set up SPI interface as follows:
SPI Mode1 (clock idle low, data transmitted on clock leading edge).
Set SPI frequency to between 300 kHz and 750 kHz.
2. SPI Master system must drive MOSI and SCK and SS communication lines.
3. Delay between a command byte and any subsequent bytes of an SPI communication should
be > 10 ms (< 100 ms).

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4. Delay between final byte of one SPI communication and first byte (command byte) of the
next SPI communication should be > 10 ms (< 100 ms).
5. Interval between bytes following the command byte of an SPI communication should be > 10
µs (< 100 µs).
6. Under certain circumstances the intervals may need to be longer i.e. the interval between
one 'Get Histogram' communication sequence and the next should be greater than 0.5 s and
ideally between 30-60 s to give a good average and smoother data. The interval after a
'Switch Peripherals/Fan on' sequence should be > 600 ms (< 2 s) to allow the firmware time
to perform multiple attempts to switch the fan on.
Normally users should allow a much longer time than this anyway e.g. 5-10 s to allow the fan
to get up to speed. Following power-up, the OPC should be allowed at least
2 s to initialise before beginning SPI communication.
7. The first histogram data set in a session, or the first histogram obtained after any kind of
error condition has passed, will have been recorded over an unknown sampling period and
should be discarded.
8. The timings and SPI frequencies specified are guidelines only. Users may experiment with
different timings at their own risk.
9. The SS connection to the OPC should be driven LOW during any SPI communication with
the OPC.
OPC SPI Commands
A full list of current SPI commands given in 072-0501 Supplemental SPI information for OPC R1, a
summary is listed in Appendix D. Further information is available from Alphasense directly.
8 Using the Alphasense Software
The software and necessary drivers to run the OPC from a computer (PC only) will be supplied with
the unit initially, in the future it will be available from the Alphasense Website.
Full guided examples for installation using Microsoft Windows XP, 7, 8, 8.1 and 10 are given in
Appendix B. We recommend that the Windows PC is running .NET version 3.5 or above.
Connecting the device and running the software
Connect the USB-SPI interface lead and OPC device to the PC. If you are prompted for device
drivers refer to the previous section of the user manual. Double click the OPC-R1.exe icon to start
the software application. When the application is first started the main form will be in “start-up
mode”as shown in the next section.
Connect to the OPC-R1 by choosing the virtual COM port it is assigned to. Some text should
appear in the software’s main text box indicating details of the OPC on successful connection. At
this stage the OPC electronics are in default mode and the laser and the fan are switched off. Press
Ctrl+R to read the configuration variables stored on the OPC.
There is no uninstall function for the software interface. The interface is stored as a set of files in a
single folder (to be kept intact) and will run as a normal Windows application. The entire folder can
be deleted or archived when redundant.

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Data Display Screens and taking Measurements
Default start-up screen
Select the allocated COM port: A list of COM ports available on the PC/Laptop is displayed in the
drop-down menu at the bottom-left of the screen. Select the correct port number; the software will
not respond unless the port with the attached OPC-R1 device is selected.
·Device information (Right hand side text window): This shows hardware serial number and
firmware versions currently installed on the OPC-R1.
·Start sampling: Starts data collection, note on the OPC-R1 this does not start the fan and
the laser. The button will then show ‘Stop sampling’to allow termination of the sampling
process.
·Laser and fan icons: Clicking the laser and fan boxes turns the lasers and fan on. Note
that changing the laser power will alter the unit’s response and will put the unit out of
calibration. Fan speed cannot be varied on the OPC-R1.
·Repeat interval ms: Sets the duration (in milliseconds) over which a particle size histogram
is acquired. The default is 1,000 ms. We recommend a maximum of 20,000 to 30,000 ms to
avoid the risk of an individual size bin becoming full (65,536 counts). Longer intervals can
be set in very clean environments.
·Y max: This sets the maximum y-axis value of the histogram screen display
·Histogram y-axis ‘Counts/ s’: This displays the recorded counts per second in each size bin,
regardless of the setting of the ‘Repeat interval ms’. For example, if a 10,000 ms sampling
interval is set, the ‘Counts/ s’figure will represent the average counts per second over that
period. This average figure is also recorded in the CSV file.
Histogram Counts/s vs Particle Size display mode
When the Start sampling button is pressed, the OPC-R1 will first ask if the data are to be saved.
Once answered, it will begin to display particle size histogram data and if selected it will store data
to a specified file.

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·Data relating to each acquired histogram, including PM values, is given in the right-hand window
of the display. The RollMean_PM10, etc., are the current rolling mean values for PM evaluated
over the previous 5 minutes or to the beginning of sampling if that is less time. The sample flow
SFR, and temperature and humidity are also given.
·Reject Glitch and RejectLong TOF are an indication of the electronic noise and errors in timing,
respectively. High values would suggest a problem with the unit or the set up.
·The total particle count rate per second across all size bins (Counts/ s) is displayed in the
bottom-left of the screen.
·Clicking on the graph and pressing ‘l’(lower case L) will display the numerical values for each
bin; pressing ‘l’again will toggle it back.
·Note: if the laser cuts out, the display will show a pattern of alternate maximum and zero count
values in bins across the whole size range of the R1, as shown below. The laser may shut
down if unusual power spikes are detected. It can be reset first by trying a stop start cycle or a
laser off and on cycle. If this is not successful then a power cycle may be required.

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Histogram Number Concentration vs Particle Size display mode
Click the ‘Histogram #/ml’button on the left-hand side of the screen to show the recorded data in
particle number concentration (particles per millilitre of sampled air) format, as below:
History Plot of Counts/s display mode
Click the ‘History plot #/s’button on the left-hand side of the screen to show a temporal record of the
particle count rate since the start of the sampling session. The plot scale will automatically change
to show longer recording time periods and/or increasing Counts/ s.

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History Plot of Mass Concentration display mode
Click the ‘Histogram plot mass conc.’Button on the left-hand side of the screen to show a temporal
record of PM1, PM2.5 and PM10 values (in µg/m3) since the start of the sampling session. The plot
scale will automatically change to show longer recording time periods and/or increasing PM values.
Data relating to each acquired histogram, including PM values, is given in the right-hand window
of the display.

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Other Software Functions
Closing down the software
It is recommended that the software application is closed before removing the USB to SPI interface
to avoid USB communication errors.
Log file
The application will also create a log file from all of the output bins into a single .CSV file. You will
be asked if you require a log file after selecting the “start”button. If you select “yes”you will be
prompted for a file name and location to store the file. An example of the log file is included in the
deployment package and the CSV output is explained later.
Firmware information
The information window on the right of the main form shows the firmware version installed as the
software first loads up. For example
Info String = OPC-R1 FirmwareVer=2.21...................................BS
Firmware is upgraded via the SPI port using a Bootloader tool, see Appendix C for more details.
More firmware commands (via software)
There are four commands that can be used to edit factory settings through the OPC software:
1. Ctrl + R: Read and display all configuration variables. This will display the variables
available to the user for edit. The data is displayed in the information window to the right of
the software window. Changeable values can be over-written in this window.
2. Ctrl + W: Write all values to configuration memory. This command will write the current
configuration values to volatile memory, this means that the user can run the OPC with their
desired configuration but the changes will be reset once the power is disconnected.
3. Ctrl + S: Save all values to configuration memory. This command will write the current
configuration values to non-volatile memory, this means that the user can permanently save
their configuration values.
4. Shift Ctrl + W: This allows the Bin weighting Index to be changed.
Changing the PM values reported
The PM values can be changed to report PM4.25 instead of one of the other PM values. Please note
only 3 values in total can be reported. To carry this out connect the OPC-R1 to the Alphasense
software as usual. Then:
1. Type Ctrl + R: Read and display all configuration variables. This will display the variables
available to the user for edit. The data is displayed in the information window to the right of
the software window.
2. Scroll to the bottom:
PM values (A, B, C) (um)
1
2.5
10
3. Overwrite one of these values with 4.25
4. Type Ctrl + W, followed by Ctrl + S.
5. The OPC will now report PM4.25

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Explanation of the CSVs
(Please note sheets are truncated to save space)
Comment
Software ver: OPC-R1 Alphasense
1.0.6473.16786
Device SerNo
SerNo: 178390116
Unit serial number
InfoString OPC-R1
FirmwareVer=2.21...................................BS
Firm ware version
Laser digital pot setting 230 Laser setting
Gain scaling coeff 1 Unused Scaling coefficient set at 1
ToF to SFR factor 87 Scaler for dynamic fan speed
correction
Bins Bin00 Bin01 Bin02 Bin03 ….. Bin15
Bin low boundary (ADC o/p) 0 9 16 23 ….. 3256 4095 Final figure is top boundary of bin
15
Bin low boundary (particle
diameter [um]) 0.35
0.7 1.1 1.5 ….. 12 12.4 Final figure is top boundary of bin
15
Bin mean (particle diameter
[um]) 0.55
0.9 1.3 1.7 ….. 12.2
Vol of a particle in bin (um3) 0.087 0.382 1.150 2.572 ….. 950.8
Weighting for bin 1.65 1.65 1.65 1.65 ….. 1.65 Individual bin weighting
Data:
OADate
Time Bin00
…
Bin15 Mean
ToF
Bin1
(us)
…Mean
ToF
Bin7
(us)
Count/s Samp
…
Period
(s)
SFR
(ml/s) #Reject Glitch #Reject Long
TOF
Temp
(C) Rel. Hum.
%
PM1
(ug/m3)
…
PM10
(ug/m3)
Roll
Mean_
PM1
…
Roll
Mean_
PM10
42341.
6282
8.001
…
0 6 …0 20.00 1 0.79 0 0 29.3 39.2 1.38
…
6.85 1.38
…
6.85
42341.
6282
5.946
…
1.982 9.33 …0 18.83 1.009 0.79 1 0 29.4 39.5 1.09
…
198.75 1.24
…
102.8
42341.
6282
8.003
…
0 7 …0 32.01 1 0.79 0 0 29.4 39.8 2.36
…
108 1.61
…
104.53
42341.
6282
7.925
…
0.991 5.67 …0 28.72 1.01 0.78 0 0 29.4 39.9 1.88
…
149.15 1.68
…
115.69
42341.
6282
8.008
…
0 6 …0 23.02 0.999 0.79 1 0 29.5 39.9 1.46
…
87.34 1.63
…
110.02
42341.
6282
11.99
7
…
0 6.67 …0 25.99 1 0.79 0 0 29.5 39.7 1.74
…
3.56 1.65
…
92.27
42341.
6282
4.954
…
0 7.67 …23 20.80 1.009 0.8 0 1 29.5 39.5 1.52
…
12.79 1.63
…
80.92
Counts per s in
each bin Used for dynamic fan compensation Total counts
per s
across
all bins
Sample
flow
through
the
OPC
Noise and
invalid particle
error indicator
Instantaneous
PM1, 2.5, 10
5 minute averaged
PM1, 2.5, 10

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9 Running the OPC R1 using direct SPI control
Full details of the SPI commands and connections are available for the OPC-R1. This is should be
sufficient for the user to be able to design their own SPI system to control the device and gather
data.
A flow chart outlining simple operation of the OPC R1 is given in 072-0501 Supplemental SPI
information for OPC-R1.
The R1 has a very low power off state unlike the OPC-N2, if the unit is placed into the low power
mode we recommend that the fan and laser are powered up for a minimum of 10 s before taking a
measurement.
10 Revision Control
Version
Comment
Release Date
Released by
A
First Draft
October 2017
Mark Giles
B
Second Draft
October 2017
Mark Giles
C
Third Draft
November 2017
Mark Giles
D
Fourth Draft
February 2018
Mark Giles
E
Fifth Draft
August 2018
Mark Giles
F
Sixth Draft
Febru
ary 2019
Mark Giles
1
Issue 1
February 2019
Mark Giles

072-0500 Alphasense User Manual
OPC-R1 Optical Particle Counter Issue 1
Alphasense Ltd Page 16 of 33 February 2019
Sensor Technology House, 300 Avenue West, Skyline 120, Great Notley. Essex.CM77 7AA. UK
Tel: [phone] - Fax: [phone]
Email: [e-mail] - Web: www.alphasense.com
Appendix A: FAQs
·Can the OPC be connected to a gas flow at 500 SCCM (or similar)?
·The OPC is designed to sample ambient air using its own fan. Connecting to a pressurised
system will alter the calibration and may also lead to deposition of particles on the inside of
the unit. The OPC is also designed to have air pulled through it rather than blown into it.
·What is the effect of low pressure (altitude)?
·Fans are constant volume devices and so, at altitude where the air density is lower, the
mass transported through the fan will be reduced but the volume is constant (assuming the
fan speed remains the same). The unit should operate normally at altitude with particle size
and number concentrations being accurate. However, when ambient temperatures are
expected to fall to below -10°C the system should be heated or well insulated to ensure
correct operation of the OPC.
·How are the units calibrated?
·The units are calibrated for sizing using controlled aerosols of monodisperse polystyrene
latex microspheres of specific sizes. Aerosol number concentration is assessed by
comparison to an OPC ‘gold standard’, previously calibrated against a certified TSI 3330
OPS instrument.
·What maintenance can be carried out on the OPC-R1?
·The OPC-R1 does not have any user-serviceable parts. The fan and laser are both chosen
to give good lifetimes. The flow path is designed to minimise particle deposition on any
internal surfaces of the OPC. The unit must not be opened for cleaning as this may expose
the worker to class 3B-laser radiation and could affect the calibration. Careful cleaning with
compressed air may be successful but this should be discussed with Alphasense
·Raspberry Pi and Arduino
·The OPC-R1 is ideally suited to be operated by devices such as Raspberry Pi or Arduino via
its SPI interface. While Alphasense does not distribute OPC-R1 control programs to be
used on these devices, many of its customers have successfully implemented such control
programs following the OPC-R1 SPI commands list.

072-0500 Alphasense User Manual
OPC-R1 Optical Particle Counter Issue 1
Alphasense Ltd Page 17 of 33 February 2019
Sensor Technology House, 300 Avenue West, Skyline 120, Great Notley. Essex.CM77 7AA. UK
Tel: [phone] - Fax: [phone]
Email: [e-mail] - Web: www.alphasense.com
Appendix B: Installing the device driver (drivers unchanged from OPC-
N2)
Windows XP
Copy the folder “OPC Interface Software”to the
PC desktop. Connect the USB interface lead to
the PC. If the USB interface lead (USB to SPI
converter) is connected to the PC for the first
time, Windows will need a device driver and this
will start the “Found New Hardware”wizard.
Select the “Yes, this time only”option and click
next.
The following window will give you an option as
to whether to use a CD to install the device
driver or to use another location. Select “Install
from a list or a specific location (Advanced)”.
Navigate to the OPC folder containing the folder
named “USB Driver”, this contains the file
devtech2.inf needed to drive the OPC device.
Click OK to allow Windows to locate and install
the device driver. This process is automatic but
you will be prompted by the form below to
confirm the installation.
Click “Continue Anyway”to finish the installation.
Once the device driver is installed correctly, the
OPC device should appear in the Device
Manager window as a “Communication Port”
with an assigned COM port number. Make a
note of this assigned port number, as you will
need it when starting the software.
The Driver installation is now complete.

072-0500 Alphasense User Manual
OPC-R1 Optical Particle Counter Issue 1
Alphasense Ltd Page 18 of 33 February 2019
Sensor Technology House, 300 Avenue West, Skyline 120, Great Notley. Essex.CM77 7AA. UK
Tel: [phone] - Fax: [phone]
Email: [e-mail] - Web: www.alphasense.com
Windows 7
Copy the folder “OPC Interface
Software”to the PC desktop.
Connect the USB interface lead to
the PC. If the USB interface lead
(USB to SPI converter) is connected
to the PC for the first time, Windows
will need a device driver.
Open the system properties and
locate the device manager.
Windows 7 will show the new device
as “USB-ISS”with a yellow
exclamation mark indicating a driver
problem.

072-0500 Alphasense User Manual
OPC-R1 Optical Particle Counter Issue 1
Alphasense Ltd Page 19 of 33 February 2019
Sensor Technology House, 300 Avenue West, Skyline 120, Great Notley. Essex.CM77 7AA. UK
Tel: [phone] - Fax: [phone]
Email: [e-mail] - Web: www.alphasense.com
Right click the icon and select
“Update Driver Software”.
Select the “Browse my computer for
driver software”option.
Navigate to the folder “OPC
Interface Software”copied to your
desktop and locate the folder named
“USB Driver”, Click Next.

072-0500 Alphasense User Manual
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Alphasense Ltd Page 20 of 33 February 2019
Sensor Technology House, 300 Avenue West, Skyline 120, Great Notley. Essex.CM77 7AA. UK
Tel: [phone] - Fax: [phone]
Email: [e-mail] - Web: www.alphasense.com
Windows 7 will then issue a security
warning. This is due to a licence
issue and not a concern to the
operating system. Select the “Install
this driver software anyway”option.
Windows will then install the driver
files for the device.
Once the device driver software has
been installed the form below will be
displayed. Make a note of the
allocated COM port number (COM4
in the example below).
If the device driver is installed
incorrectly the Device Manager will
indicate this with a yellow
exclamation mark symbol shown
below.
If this should happen, remove the
USB lead and uninstall the device
by right clicking the symbol and
selecting “Uninstall”. Return to the
beginning of the “Installing the
device driver”(Windows XP or
Windows 7) section.