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Abstract
The original version of the continuous flow counter has been improved and redesigned to run automatically with a rotary sequencing valve and data processing system. As previously described, the counter was developed at the Environmental Measurements Laboratory for use with diffusion batteries because they require a constant flow of aerosol for particle size measurement. The automated system is used extensively for measurement of the concentration and particle size distribution of indoor and outdoor aerosols. The operating conditions are evaluated to determine the effect of temperature deviation and alcohol dilution. Laboratory measurements of both the dew point and the light transmission show the diameter of the alcohol drops to vary from 13 μm at nucleus concentration of 1000/cm3 to 5.5 μm at 300,000/cm3. A recent calibration shows the new counter to be nearly 100% efficient for condensation nuclei ranging from 90 to 5 nm in diameter.