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Microscopic Measurement of Particle Size. Reading: Chap 20. Q: How do you determine this particle’s size?. Equivalent sizes of Irregular Particles ( 2-d ) Martin’s diameter: Feret’s diameter: Projected area diameter:. Q: Orientation?. Calibration. Porton Graticule

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Microscopic Measurement of Particle Size

Reading: Chap 20

Q: How do you determine this particle’s size?

  • Equivalent sizes of Irregular Particles (2-d)

    • Martin’s diameter:

    • Feret’s diameter:

    • Projected area diameter:

Q: Orientation?

Aerosol & Particulate Research Lab


Porton Graticule

(printed on eye piece)

Stage Micrometer (calibration standard printed on glass slide): distance between the smallest lines is 10 mm.

A-F is 200 times of d0.

Aerosol & Particulate Research Lab

Stratified counting
Stratified Counting

Many aerosol size distributions are skewed, and relatively few large particles are present. Counting a meaningful number of large particles involves counting unnecessarily large numbers of small particles

Q: How to avoid it?

Aerosol & Particulate Research Lab

Volume shape factor
Volume Shape Factor

Projected area diameter

Equivalent volume diameter

Shape factor can also be defined for surface area.

Aerosol & Particulate Research Lab

Spreading factor
Spreading Factor

Liquid aerosol particle are spherical when airborne, but they spread out to form a lens-shaped droplet when collected on a glass slide

Q: How to reduce the spreading?

Airborne size

On slide


Aerosol & Particulate Research Lab

Q: How long is FL’s coastline?

Degussa P25 TiO2 particles

TI 1243

Aerosol & Particulate Research Lab


Borders of clouds and smoke plumes

Geometry of lung airways

Aerosol & Particulate Research Lab

Fractal Dimension

Self-similarity at different levels of magnification

L: total length

: step size

Df: fractal dimension

Q: Df = 1? 2? 3?

For agglomerates,

Npp: Number of primary particles

Rg: radius of gyration (rms average distance the particle’s mass is from its center of mass)

dpp: diameter of primary particles

Aerosol & Particulate Research Lab




Agglomerates formed by different mechanisms

Q: How to change from compact-solid to fluffy?

Smoke, Dust and Haze,

Friedlander, 2000

Aerosol & Particulate Research Lab


Aerosol & Particulate Research Lab