Calibration of PMP Condensation Particle Number Counters: Effect of Material on Linearity and Counting Efficiency

Recently the particle number method was proposed to the light duty regulation, so the proper calibration of Particle Number Counters (PNCs) will be very important. Calibration includes the linearity measurement and the counting efficiency measurement. Labs will have to demonstrate compliance of their PNCs with a traceable standard within a 12 month period prior to the emissions test. Compliance can be demonstrated by: -Primary method: By comparison of the response of the PNC under calibration with that of a calibrated aerosol electrometer when simultaneously sampling electrostatically classified calibration particles, or -Secondary method: By comparison of the response of the PNC under calibration with that of a second PNC which has been directly calibrated by the above method. Compliance testing includes linearity and detection efficiency with particles of 23 nm electrical mobility diameter. A check of the counting efficiency with 41 nm particles is not required. A workshop was organised to investigate the effect of the material on the calibration procedures and the uncertainties of the suggested procedure.