Determination of the particle size and particle number in the outside air by means of a new optical aerosol spectrometer

Optical aerosol spectrometers offer many advantages for the particle measurement in outside air. They must, however, fulfil certain technical conditions in order to ensure significant measurement results. The described theoretical basics related to counting optical particle measuring methods illustrate the importance of good device characteristics, e.g. a high resolution and a good classifying accuracy which are reached by a clear calibration curve and a measurement without border zone errors. The new white light aerosol spectrometer welas((R))-system is very well suitable for atmospheric measurements not only due to optimal device characteristics, but also due to its patented modular structure which allows measurements in hardly accessible environments, e.g. in the troposphere down to -90 degrees C. In the following, we will describe the operational principle of the t-aperture-technology which is applied for patent and we will introduce the welas((R))-system 3000 as our newest development. The welas((R)) 3000 can measure quasi simultaneously with two sensors connected to one control unit the outside air at two different places at the same time. The measuring range of the welas((R)) spectrometer covers the transition area between the two particle counting techniques of the condensation nucleus counter and the microscope-based coarse particle counting with the Sigma-2. The combination of these counting techniques in connection with gravimetric methods may open up a new approach to the study of optical, morphologic, and aerodynamic properties of the atmospheric aerosol.