The AethLabs microAeth? AE51 is a high sensitivity, miniature, portable instrument designed for measuring

the optically-absorbing Black Carbon (‘BC’) component of aerosol particles. The instrument is based on the

well-established Aethalometer principle used for over 30 years in laboratory-sized analyzers.

The microAeth AE51 draws an air sample at a flow rate of 50, 100, 150 or 200 ml/min through a 3 mm

diameter portion of filter media. Optical transmission through the ‘Sensing’ spot is measured by a stabilized

880 nm LED light source and photo diode detector. The absorbance (‘Attenuation, ATN’) of the spot is

measured relative to an adjacent ‘Reference’ portion of the filter once per timebase period. The gradual

accumulation of optically-absorbing particles leads to a gradual increase in ATN from one period to the

next. The air flow rate through the spot is measured by a mass flow sensor which is also used to stabilize

the pump. The electronics and microprocessor measure and store the data each period to determine

the increment during each timebase. This is then converted to a mass concentration of BC expressed in

nanograms per cubic meter (ng/m3) using the known optical absorbance per unit mass of Black Carbon

material.

The instrument’s operating parameters are set up by an external software application (microAethCOM)

and uploaded to the microAeth AE51 by a USB interface cable. Operation is completely automatic after

the instrument is switched on. During operation, the microprocessor performs the optical measurements,

measures and stabilizes the air flow, calculates the BC mass concentration and records data to internal nonvolatile

memory. The data may be downloaded at a later time by the same external software package.

The microAeth AE51 derives its power from an internal rechargeable battery. The same USB interface cable

serves to recharge the battery from either the USB port of a connected external computer, or an AC power

supply. The instrument will operate for 6 to 24 hours on a single charge, depending on operational settings.