Multi Channel Aerosol Sampling System
The Multi Channel Aerosol Sampling System (ASSAY) was developed to provide year long sampling of airborne aerosol particles. The project brief demanded operation in extreme Antarctic conditions without any operator intervention. Samples would be collected during a single site visit to remove any possibility of contamination.The system consisted of an air pump, airflow meter, timing system and filter holder. Air was drawn over the filter paper located at the top of the air intakes - shown under the "mushroom" head. The copper down pipes held a form of silica gel to remove water vapour before entering the flow meter and pump.
Each pump channel consumes around 100mA and the airflow meter another 10mA. The electronics was based on discrete logic as it was felt that using a microcontroller would make field repairs/changes difficult. The control logic current for each channel was reduced to a few hundred uA.A total of 18 x 100AH batteries were deployed, this is quite a lot, but
at -30C the batteries will only provide around 50% of their rated capacity and a good safety margin had to be built in to cope with solar panel failure.
During the first year it was noticed that frost buildup was a major concern, so the system was changed to allow the inlet pipes to move in the wind thus dislodging most of the ice.