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Short Name or Variable Name:
RDMA
HAIS Instrument:
No
Manufacturer or Builder:
Constructed at RAF from a mix of commercial and custom fabricated components
TABS
Description
Model:
none
Measurements Provided:
Size distribution and concentration of aerosol particles ~7 to 200 nm diameter in 64 size bins, 10 sps
General Description:
RDMA is a continuous-flow instrument that measures aerosol particle electrical mobility distributions that correspond to particles ~7 nm to ~200 nm diameter. The exact size range depends on flow rate, voltages, air pressure and temperature. The air sample passes through an ion source where the aerosol particles acquire an electrical charge. Particles with the correct charge and mobility are selected in a parallel-plate precipitator, where a voltage is imposed between the plates, then counted with a CN counter. The selected size changes continuously by ramping the voltage through a large range, ~30 to 6000 volts over ~160 s period. RDMA requires an air sample inlet and piping.
Measurement Characteristics:
Overall estimate of uncertainty:
Response time: each up/down voltage scan cycle takes ~160 sec and produces two size distributions
Precision: 64 size bins in logarithmic increasing sequence, 7 to 200 nm diameter
Other measurement characteristics (comments on signal/noise, bias limits, etc):
Sampling is affected by particle diffusion losses, size-dependent charging efficiency, splash/breakup artifacts at the inlet tip, and humidity.
Calibration Methods:
Monodisperse PSL for size, Gilibrator for flow, RAF standards for P, T, RH
Contacts
Lead Contact:
Mike Reeves
Status/Plans
Current Location:
Not Available
Operational Status:
Decommissioned ( no longer requestable )
Serial Numbers
Property Tag and/or Serial Number:
Not Available
Radial Differential Mobility Analyzer
Organizational Facilities
Research Aviation Facility (RAF)
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