Application and performance test of a micro-machined unipolar charger for real-time measurements of exhaust particles from a diesel engine vehicle

Characterization of particulate matter (PM) emitted from diesel vehicle exhaust requires a real-time measurement sensor to record particle concentrations under transient tests. Recently, a micro-machined unipolar charger (MUC) based on a micro-electromechanical system (MEMS) was introduced and evaluated to test aerosol particles on a laboratory scale. We present the performance characteristics of the MUC for its potential use as a sensor for diesel PM emissions. A correlation equation was derived from particle loss experiments and tandem differential mobility analyzer (TDMA) measurements in the laboratory, which was used to convert the current measurement datum into a total particle number concentration. Under various idling and driving conditions of a diesel vehicle, the electrical signals from the MUC were verified to have followed the trend of the total number concentrations of diesel PM measured using a condensation particle counter (CPC). When the diesel PM concentrations measured using the CPC were within the range of 2×104–2×105 #/cm3, the total number concentrations, estimated using a correlation equation, were in agreement with the CPC data.