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: +44 (0) 1376 556700 - Fax: +44 (0) 1376 335899
Email: [email protected] - 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.
