An automatic particle analyser system using an off-line digital computer

An investigation of an automatic particle analyzer which measures the size distribution and the mean diameters of atomized liquid droplets was carried out. The scheme of the whole system was as follows. A photograph of particles was put on a drum which rotated at a constant speed and was scanned with a focused light beam. The signals, corresponding to the brightness of the photograph, were detected and converted directly into digital signals. These signals were processed through a subsequent digital circuit, in which they were converted into decimal digits and punched out on paper tape. The data, via punched tape, were put into the digital computer and computed according to an appropriate program. High accuracy, resolving power and stability were achieved by this system which was composed of a digital circuit for all signal manipulations after the scanning apparatus. Furthermore, the use of a digital computer for droplet recognition improves recognition capacity. Consequently, it became possible to recognize the annular patterned shadows, which are one of the characteristics of transparent liquid droplets like water, which were impossible to analyze hitherto.