Characterization and Performance of a Low-Cost, Open Source Condensation Particle Counter (CPC)
AARON COLLINS, OpenAeros LLC
Abstract Number: 418
Working Group: Instrumentation and Methods
Abstract
As concern over ultrafine particles and the creation of particle-number-based standards become a priority in the regulatory framework around air quality, issues around broadly accessible and scalable instrumentation have come to the fore-front. OpenCPC – a low-cost and open source condensation particle counter – has been developed to help bridge the gap between low-cost optical counters often used for community monitoring that typically can’t measure ultrafine particles and high-performance but more costly lab grade CPCs.
The OpenCPC offers a low-cost optical design, featuring a lensless scattered light collection system and a tightly focused laser beam smaller than the nozzle diameter. Implications of counting only a fraction of the aerosol exiting the nozzle and particle-size-dependent counting efficiency is explored in this work. To overcome these challenges, a newly developed correction algorithm allows for both particle size and fractional counting to be corrected by a simple process. Measurements of concentration linearity to reference devices (a TSI 3025a and a faraday cup electrometer) are performed over the range of 10 to 150,000 particles/cm3 to validate the performance of the correction methods.
One defining feature of a CPC is the particle-size-dependent counting efficiency for an incoming aerosol, often termed the cut-off curve. For laminar flow designs, such as the OpenCPC, this curve is proportional to the temperature difference between the saturator and condenser, and material composition of the aerosol. In this work we explore the performance of the OpenCPC over a range of saturator and condenser temperatures using monodisperse aerosol comprising different materials. These empirical results are used to help close a computational fluid dynamics model of the OpenCPC over the tested temperature ranges.
This work was supported by a gift from the Balvi Philanthropic Fund and by contributions from M. Pang, R. Andreasen, C. Libby, L. Goessling, and J. Stam.