072-0500 Alphasense User Manual
OPC-R1 Optical Particle Counter Issue 1
Alphasense Ltd Page 7 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: sensors@alphasense.com - Web: www.alphasense.com
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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