AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
SEMS Transfer Function Calculation for Fast Up- and Down-scan Operation
MARK KANAPARTHI, Suresh Dhaniyala, Clarkson University
Abstract Number: 434 Working Group: Instrumentation and Methods
Abstract The Scanning Electrical Mobility Spectrometer (SEMS) is a popular instrument for sub-500nm aerosol size distributions measurements. The SEMS is operated with an exponentially increasing voltage step (up-scan) followed by an exponentially decreasing voltage step (down-scan). The classification characteristics of an SEMS instrument under an up-scan operation can be computed via a semi-theoretical approach. The approach involves calculating the arrival-time transfer function (ATF) of particles of one mobility and then transforming the time-based ATF to a mobility-based DMA transfer function. In our current work, we extend the original ATF approach to calculate the DMA mobility transfer function under down-scan operation. We will present the dependence of down-scan transfer function characteristics on DMA operating conditions. As the ATF-based calculation approach is only valid for particles that are injected after the commencement of the scan and that arrive before the scan ends, this approach cannot entirely describe the DMA transfer function characteristics under fast-scan operation. Here, using a combination of the ATF approach and a series representation of the up and down voltage step, we demonstrate the possibility of obtaining SEMS classification characteristics for the entire duration of the up- and down-scan operation for all SEMS operating conditions. We demonstrate that this approach helps establish a relationship between SEMS operating conditions and effective time periods at which invertible data can be obtained.