The Community Ruggedised Optical Particle Counter (CROPC) was developed with the intention of operating it on the UK’s Facility for Airborne Atmospheric Measurements. It would have been a replacement for the Passive Cavity Aerosol Spectrometer Probe (PCASP). While the PCASP has a long heritage as the de-facto standard high-sensitivity optical particle counter, we felt we could build a more reliable instrument with similar sensitivity.
The prototype has been built by taking a PCASP optical block and stripping away all the old technology, to be replaced with modern detectors and laser technology. We retain the heritage of the PCASP, with its short focal length parabolic mirror that wraps around the aerosol sample, and we’ve brought it into the modern era.
The sad closure of the Facility for Airborne Atmospheric Measurements means we’ve started to look elsewhere for uses of the CROPC, with a commercial instrument in the works. The specification of our current prototype is as follows:
Minimum detectable particle diameter: 100 nm
Time resolution: better than 20 μs – every particle is timestamped
Size bins: configurable up to 16,384
Weight: under 2 kg, without an enclosure
Size: About the size of a lunchbox
Calibration method: nebulised polystyrene latex (PSL) nanospheres
Laser power: 3W
Laser wavelength: 600 nm
Scattering angle range: 35-120°
Collecting optics focal distance: 5 mm
Sample rate: 1 cm3 s-1 (tuneable)