Improved sequencing system for sampling clean gases to obtain particle size distributions with a diffusion battery and a condensation nucleus counter

Experience with the combination of a diffusion battery and a condensation nucleus counter (CNC) showed the need for lowering the background counts due to particle generation within the sample sequencing mechanism of one commercial switching valve. An improved sample sequencing system was developed, based on a modular series of gas-operated solenoid valves. It produced fewer spurious particle counts and allowed very accurate and flexible sample durations to be preset.