Model PAS 2200CE - Photoelectric Aerosol Sensor (PAS) Brochure

The PAS 2000 works on the following principles: Using an Excimer lamp the aerosol flow is exposed to UV radiation. The Excimer lamp offers a high intensity, narrowband source of UV radiation. The wavelength of the light is chosen such that only the carbon aerosols are ionized, while gas molecules and non-carbon aerosols remain neutral. The carbon aerosol particles emit electrons, which are subsequently removed when an electric field is applied.  The remaining positively charged particles are collected on a filter inside an electrometer, where the charge is measured. The resulting electric current establishes a signal, which is proportional to the concentration of Elemental Carbon and/ or PAH. Also by operating the Excimer lamp in a chopped mode, the PAS 2000 can eliminate the background signal, which is associated with freshly generated aerosols. The chopped mode also enables a dynamic zero to be generated automatically by the instrument.