> For the complete documentation index, see [llms.txt](https://docs.aethlabs.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.aethlabs.com/microaethalometer-tm-ma600/manual/appendix-e-glossary.md).

# Appendix B: Glossary

Definitions of key terms used throughout the microAethalometer™ MA600 Operating Manual.

| Term            | Definition                                                                                                                                                                                                                                                                               |
| --------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| AAE             | Absorption Angstrom Exponent. Describes the wavelength dependence of aerosol light absorption. Used in source apportionment to distinguish fossil fuel (AAE ≈ 1.0) from biomass burning (AAE ≈ 1.5–2.5).                                                                                 |
| ATN             | Attenuation. A dimensionless quantity describing the optical loading of the filter tape at each wavelength. The primary raw measurement from which BC is derived. ATN increases as aerosol accumulates on the filter.                                                                    |
| AutoSample      | An instrument setting that causes sampling to start automatically when the instrument powers on. Recommended for unattended deployments.                                                                                                                                                 |
| BC              | Black Carbon. Light-absorbing carbonaceous aerosol, primarily from combustion. Measured at 880 nm (IR channel).                                                                                                                                                                          |
| BC1             | BC calculated from the Spot 1 (sense1, primary) spot. Available in SingleSpot™ and DualSpot® modes.                                                                                                                                                                                      |
| BC2             | BC calculated from the Spot 2 (sense2, secondary) spot. Available in DualSpot® mode only.                                                                                                                                                                                                |
| BCc             | Loading-compensated BC, computed for each wavelength from BC1, the DualSpot® loading-compensation factor K, and the attenuation ATN1. Recommended output for most applications.                                                                                                          |
| Cref            | Reference cross-section value used in source apportionment calculations. Default value for PTFE filter is \~1.3.                                                                                                                                                                         |
| DualSpot®       | Real-time loading compensation method using two filter spots sampled simultaneously at different flow rates to calculate and correct for the loading artifact.                                                                                                                           |
| K               | Loading compensation factor calculated from the difference in attenuation between the DualSpot® Spot 1 and Spot 2 (sense1 and sense2) spots. Applied to BC1 to produce BCc.                                                                                                              |
| ONA             | Optimized Noise Algorithm. A post-processing algorithm that can be applied to MA Series data to reduce noise in the BC output. Available in microAeth® Manager.                                                                                                                          |
| SA              | Source Apportionment. The process of estimating the contributions from different aerosol sources using multi-wavelength optical data. The MA600 computes SA in real time using the AAE method when DualSpot® is enabled and the required wavelengths (IR + Blue, at minimum) are active. |
| SingleSpot™     | Sampling mode using only one filter spot (Spot 1 / sense1) at the full configured flow rate. No loading compensation; no source apportionment.                                                                                                                                           |
| Spot 1 (sense1) | The primary optical sampling spot. In SingleSpot™ mode, only Spot 1 is used. In DualSpot® mode, Spot 1 runs at the higher flow rate (75% of total).                                                                                                                                      |
| Spot 2 (sense2) | The secondary optical sampling spot. Only active in DualSpot® mode. Runs at the lower flow rate (25% of total flow).                                                                                                                                                                     |
| Timebase        | The measurement interval in seconds. One data row is produced per timebase period.                                                                                                                                                                                                       |
| UVPM            | Ultraviolet Particulate Matter. The BC-equivalent concentration measured at 375 nm. Particularly sensitive to light-absorbing organic aerosol from biomass burning, tobacco, and other non-fossil sources.                                                                               |

***

*microAeth® and microAethalometer™ MA Series products are protected by patent #8,411,272. Additional patents pending.*

*microAeth® is a registered trademark of microAeth Corporation dba AethLabs.*

*Aethalometer® and DualSpot® are trademarks of Magee Scientific Corporation used under license.*

*microAethalometer™ MA600 Operating Manual, Rev01*