Characterization of an Augmented Version of the Printed Optical Particle Spectrometer for Integration into Multi-Instrument Aerosol Sampling Systems
SABIN KASPAROGLU, Mohammad Maksimul Islam, Nicholas Meskhidze, Markus Petters,
North Carolina State University Abstract Number: 147
Working Group: Instrumentation and Methods
AbstractThe Printed Optical Particle Spectrometer (POPS) is a light-weight, low-cost instrument for aerosol number concentrations and size distributions measurements. Here we report on modifications of the Handix Scientific commercial version of the POPS to facilitate its use in multi-instrument aerosol sampling systems. The flow system is modified by replacing the internal pump with a needle valve and a vacuum pump. The instrument is integrated into closed-flow systems by routing the sheath flow from filtered inlet air. A high-precision multichannel analyzer card (MCA) is added to sample the analog pulse signal. The MCA card is polled at 10 Hz frequency using an external data acquisition system and removes the count-rate limitation of 10,000 particles s
-1 associated with the POPS internal data acquisition system. The MCA card enables integration of the POPS into larger setups that require precise time stamping and clock synchronization, especially in field measurements (e.g. eddy-covariance flux measurements, aircraft sampling). The 90/10 rise and fall times were measured to be 0.17 s and 0.41 s at a flow rate of 5 cm
-3 s
-1 and provide a sampling frequency of ~1-2 Hz below which the amplitude of measured fluctuations is captured with > 70% efficiency. We also integrated the POPS into the dual tandem DMA system, which generates dimer particles. We show that the pulse-height response increases upon dimer coalescence. The magnitude of the increase is broadly consistent with the change in light scattering amplitude predicted by the T-matrix method, which can be used to detect phase transitions occurring in agglomerated particles. We anticipate that this augmented version will extend utilization of the POPS for field and laboratory applications.