Electronic Instrumentation of a Device to Automatically Count and Size Particles in a Gas

This paper describes the electronic instrumentation of a device called an aerosoloscope for automatic counting and sizing of aerosol particles. This device relieves the chemist of the tedious and time-consuming job of counting the particles collected on a slide under the microscope. It has wide potential application in analyzing dusts fogs, smokes, etc. Particles from one to 64 microns in diameter and counting rates up to 100 particles per second are handled by the instrument. The aerosol is diluted and drawn across a high intensity light beam; a multiplier phototube receives a portion of the light energy scattered by each particle. The resulting electrical pulses are amplified and classified by size into 12 groups by a unique pulse height discriminator. Glow-transfer tubes and registers are used to count the pulses within the various groups. Dynamic range problems and system noise are briefly discussed.