An Automatic Pollak Counter Improved for Routine Field Operation

Abstract

An automatic aerosol counter is developed as a monitoring instrument for the atmospheric pollution level in an area. The counter is essentially similar to the 1957 Pollak counter with a slightly convergent light pencil and with under-pressure expansion. The present counter is characterized by its fog tube which consists of a single unit ceramic tube directly jacketed with water flowing at constant temperature so as to maintain the temperature and the humidity of the air sample just before expansion in the fog tube at the constant value irrespective of the ambient conditions throughout the period of long-term field operation. With the present counter, reliable aerosol concentration can be obtained every six minutes within ±10% of measured value, continually for a period of more than one year.
In the present paper are described the details of improvements made on the Pollak type counter for long-term field observation and the performance of the improved instrument. An example is also shown of the results of field observation for one year with the present counter.