Radial Differential Mobility Analyzer | Earth Observing Laboratory

Short Name or Variable Name:

RDMA

HAIS Instrument:

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