SAMPLE STREAM DRYER

Drying the aerosol sample stream is highly recommended to provide accurate measurement data and to protect the equipment from water condensation.

In hot, humid locations, the water vapor content of the ambient sample air may be very large.  This can lead to inaccuracies in the BC measurement – but, more seriously, there is the possibility of water condensation inside the instrument which can lead to permanent damage.  This issue is solved by the use of our Sample Stream Dryer.

The interaction of water with aerosol species changes their physical properties.  Consequently, the World Meteorological Organization has recommended that all aerosol measurements should be performed under conditions where the Relative Humidity is 40% or lower (WMO/GAW 2003; Wiedensohler, 2014).

Many stations in hot, humid locations have air-conditioned interiors.  If the indoor air-conditioning temperature T_a is comparable to or lower than the dewpoint (condensation temperature) T_d of the outside ambient air, water will condense in the tubing and inside the instrument.  This will not only completely in-validate the data, but it can also cause permanent damage to the instrument.

The Magee Scientific Sample Stream Dryer removes water vapor from the inlet flow by means of a semi-permeable Nafion membrane.  This membrane selectively absorbs molecules of water vapor from the air-stream and passes them to a space on the other side of the membrane, maintained at a low absolute pressure by means of a vacuum pump.

The Magee Scientific Sample Stream Dryer can reduce the dew point temperature by up to 14 degrees Celsius at a flow rate of 5 LPM.  The equipment is self-contained, automatic, and includes a display screen which shows the input and output hygrometric properties.  A data cable can connect to the Model AE33 Aethalometer so that the temperature and humidity data are incorporated into the Aethalometer’s data files.

The Magee Scientific Sample Stream Dryer can be used to remove water vapor from the inlet stream to any aerosol instrument, not just an Aethalometer.

• Magee_Scientific_Sample_Inlet_Dryer_brochure_sheet_A4
• Magee_Scientific_Sample_Inlet_Dryer
• Magee_Scientific_ Aethalometer_AE33_Sample_Inlet_Dryer_installation

NEUTRAL DENSITY OPTICAL VALIDATION KIT

The Neutral Density Optical Filter Kit provides validation of the reproducibility of the photometric detectors.

The optical performance of the Model AE33 Aethalometer may be validated in the field by the ‘Neutral Density Optical Filter Kit’, consisting of four precision optical elements containing precision glass whose absorbance is traceable to primary photometric standards maintained by national organizations such as NIST (USA), NPL (UK), BIPM (EU), etc.  Software routines measure the optical intensities at all wavelengths and compare the analysis during the test, with the original reference values.  This validates the reproducibility of the Aethalometer’s fundamental measurement of optical Attenuation.

• Magee_Scientific_Aethalometer_AE33_ND_Optical_Validation_Kit
• Magee_Scientific_Aethalometer_AE33_accesories_brochure_sheet_A4

AMBIENT METEOROLOGICAL SENSOR

The Ambient Meteorological Sensor is a non-aspirated unit which measures air temperature, relative humidity and barometric pressure.  It uses a Pt100 element for Temperature; a compensated solid-state capacitive sensor for Relative Humidity; and a piezo-resistive pressure transducer for Pressure.  The sensing elements are protected by a UV-resistant polymer shield.  A data cable (supplied in 10-m. or 20-m. lengths) connects the sensor to the AE33, and its data is automatically imported and merged with the Black Carbon measurements.

• Meteorological_weather_Station_TPR_159_spec_sheet
• Meteorological_weather_Station_TPR_159_user_manual
• Magee_Scientific_Aethalometer_AE33_accesories_brochure_sheet_A4

FILTER TAPE

The Model AE33 Aethalometer collects its samples on a proprietary filter tape made of glass fibers coated with PTFE/PET, and supported on a mechanical backing for transport in the instrument.  When the spot reaches a pre-set loading density, the tape is advanced to create a new spot.  Each roll of tape is 10 m. in length and will last from a few weeks to a few months, depending on the average concentration of BC in the sampled atmosphere and the operational flow-rate that is chosen.

SIZE-SELECTIVE INLETS

Ambient atmospheres include suspended particles of large aerodynamic size such as pollen, dust, etc.  These particles are not strongly optically absorbing and therefore do not interfere with the Aethalometer® analysis: however, after lengthy use a deposit of dust in the internal optics will degrade performance.  To exclude large particles, and to provide analysis of a known respirable size fraction, we recommend use of size-selective inlets designed to exclude particles of aerodynamic size greater than a specified cut point at a specified sample air flow rate.  We offer the ‘Sharp-Cut Cyclones’ designed by BGI (USA) and now manufactured by Mesa Labs (USA).  These inlets are usually attached directly to the sample inlet tube at the point of entry, but may also be installed in-line closer to the Aethalometer..

PM2.5 Inlet
BGI model SCC-1.828.  Provides a cut point of 2.5µm at a sample flow rate of 5 LPM.

PM1/2.5 Inlet
BGI model SCC-1.197.  Provides a cut point of 2.5µm at a sample flow rate of 2 LPM, or 1µm at a sample flow rate of 5 LPM.

PM1 Inlet
BGI model SCC-0.732.  Provides a cut point of 1µm at a sample flow rate of 2 LPM.

BGI ‘Mini-PM’ Inlet Kit
The BGI ‘Mini-PM’ Inlet Kit offers impaction jet inserts to provide size selective capabilities of TSP, PM-4, PM-2.5, and PM-1, when operated at a flow rate of 5 LPM.

TRANSIT CASE

For situations where the Aethalometer® must be shipped or transported frequently, we recommend the use of Pelican® transit cases.  These provide internal padding; a sturdy waterproof exterior; and integrated retractable handle and roller wheels.