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Differential Mobility Analyser


DOS AND DON'TS

DO make sure all connections are tight.

DO attach the DMA first, then switch on the CPC. If attachments are made with the CPC turned on, it won't recognise the connection to the DMA until the Windows software provides a reboot instruction.

DO remove the nozzle of the impactor with the nozzle tool (situated above the impactor on the DMA) before use to check it is clean and that it is the correct device for the DMA. If the valve is blocked, it should be cleaned by having clean air blown through it, or by ultrasonic methods.

DO lightly grease the impactor before use with a thin layer of the lubricant provided to ensure the larger particles adhere to it.

DO handle the electrodes of the DMA with considerable care. They are very precisely and accurately built, and must not be dented or distorted as this will in turn distort the electric field produced within the DMA

DO remember that the DMA classifies according to mobility (which is proportional to particle size AND charge) and not simply to the size of the particles.

DON'T forget that the charges on aerosol particles will vary. The charge distribution is modelled but this model may not exactly reflect the actual charge distribution. This will affect the final reading and must be taken into consideration.

DON'T forget to check the instrument regularly to ensure it is clean and working correctly. Go through the points outlined in the Care and Maintenance section regularly to keep the instrument in good condition and ensure accurate readings are taken.

DON'T assume the instrument is always working correctly. When the CPC is in Service Mode, errors will not be reported and the instrument will continue to work even if conditions there is a fault in the system. If in doubt, check the instrument is functioning correctly by taking a reading without applying a voltage. When zero voltage is applied to the electrodes, any readings should give a zero value for the sample aerosol.

Earth Observation Data Group, Department of Physics, University of Oxford. Page last updated: @21:11 GMT 13-Apr-2014