072-0300
Alphasense User Manual
OPC-N2 Optical Particle Counter
Issue 5
Alphasense Ltd Page 17 of 34
December 2015
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
•
What are the differences between the different firmware versions
Firmware 16 and 17 including 16B and 17B
•
Firmware 18 builds on the previous firmware release 16 and 17. Please note Firmware 16 and
17 are basically equivalent, different versions were needed to support the use of two different
PCBs, issue 2 with Firmware 16 and issue 3 with 17. Similarly for version 18, 18.1 is for issue 2
and 18.2 for issue 3. In operation the only significant difference is that units with Issue 2 boards
use more power in the standby mode as the standby laser power is not as low as in issue 3.
Units with issue 2 boards must only be updated with the correct firmware as irreversible damage
to the laser may occur otherwise.
•
General running and features of 16 and 17 are the same in issue 18. All have dynamic
correction for sample flow-rate caused by changes to the of the fan speed and also apply the
respiratory profiles to the PM values
•
Issue 18 has more advanced standalone recording to the onboard SD card and some additional
commands to make it easier for end users to write their own software. The serial number of the
OPC is stored on the unit and is recorded on any CSV files.
•
Issue 18 units have, in addition a scaling factor applied to each bin to align the unit more closely
to reference detectors following co-location studies. This scaling factor can be retrofitted to units
in the field; details can be obtained by request from Alphasense.
•
It is recommended that you continue to use the initial software release in deployment versions
9.7 and 9.8 for units with firmware 16 and 17.
•
If you are running 16, 17, 16B or 17B using your own software developed for an earlier version
such as 15D please allow more time at start up before issuing the first command, ~1 s. The
main commands are the same across most releases. Data positions in the call histograms and
read functions may have changed; see the full list of commands for details.
Firmware 15D
•
There are differences in firmware commands and responses between units with 15D and later
firmware.
•
In terms of performance these units to not offer the dynamic correction of sample flow-rate for
variations in fan speed and have a simplified method of calculating the PM values
•
If you continue to use these units is recommended that you use the initial software released in
deployment 9.5.
•
It is possible to update the majority of these units in the field to firmware 18.1.
Older Units, other Firmware 15 variants and 14
Substantial improvements have been made since these units have been issued. It is not possible to
update these units in the field. Please Contact Alphasense to discuss potential upgrade options.
•
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)
•
Fundamentally, fans are constant volume devices and so, at altitude where the density of air
is lower, the mass transported through the fan will be reduced but the volume stays the
same (assuming the fan speed remains the same).
