grimm aerosol spectrometer and dust monitors measuring … · 2014-07-28 · 1 1 wolfgang...

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Wolfgang Brunnhuber , Dr. Friedhelm Schneider

GRIMM Aerosol Spectrometer GRIMM Aerosol Spectrometer

and Dust Monitorsand Dust Monitors

Measuring principleMeasuring principle

by Eng. Wolfgang Brunnhuberby Eng. Wolfgang Brunnhuber

Grimm Aerosol-Technik

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Part A

physical background

general principles of optical particle detection

Part B

Nanoparticles

counting and sizing

Agenda

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Scale [nm]

Fields:

Media

Materials

Ions Molecules Macro Mol. Micro ParticleMacro Particle Impurities Sievable

1 10 100 1,000 10,000 100,000

Light

Metal

IonsSaccharose

Virus

Activated

Carbon Dust

Colour Pigments

Bacteria

Human HairAsbestos

Diesel Soot

Grimm SMPS+CGrimm SMPS+C(DMA+CPC)

[nm]

Grimm SMPS+EGrimm SMPS+E(DMA+FCE)

modelsGrimm 1.108 / 1.109Grimm 1.108 / 1.109

physical background: particle size range

[µm]1 10 1000.10.010.001Scale [µm]

Fungal spores

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physical background: Interaction of

radiation and aerosol particles

[Seinfeld & Pandis, 1998]

αααα = ππππ dp/λλλλwith dp= particle diameter and

λλλλ = incident wavelength

note: ππππ dp = particle circumference,

for spherical particles

The interaction between incident light and a particle

(solid, droplet and or gas molecules!) is strongly

dependent on the particles size and the wavelength.

To show this dependency, the parameter αααα is used.

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physical background: dependency of

particle size and wavelength on scattering

[Baron & Willeke, 2001]

For particle sizes much smaller than the incident wavelength (αααα << 1)

RAYLEIGH-scattering: the oscillating electric field of the light waves

induce an oscillating dipole in the particle, causing symmetrical scattering

(in forward and backward directions). The Intensity of the scattered light is

proportional to the sixth power of particle diameter (I ~ dp6)

Example:

Sunlight hits gas molecules in

the atmosphere, blue sky effect!

αααα = ππππ dp/λλλλ with dp= particle diameter; and λλλλ incident wavelength

note: ππππ dp = particle circumference, for spherical particles

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For particle sizes in the size range as the incident wavelengt (depending

on the light source! say 0.1µm-1µm)

MIE-scattering: strong interaction between the particle and the incident

beam, depending although on particle refractive index. No simple relation

between scattered intensity and particle diameter (Mie-programs,

spherical particles)



Gustav Adolf Feodor Wilhelm Ludwig Mie

* 1868 † 1957

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For particle sizes much bigger than the incident wavelength (αααα >> 1)

GEOMETRIC OPTICS: light rays hitting the particle lead to reflection,

refraction and absorption, rays passing the particles edge give rise to

diffraction. The scattered intensity is proportional to the particle cross-

sectional area (I ~ dp2) and not strongly dependent on shape or particle

composition

Example:

Sunlight hits water droplets

in clouds, they appear white!



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physical background:

scattering intensity vs. particle size


particle circumference

incident wavelength=

Rayleigh

Mie

Geometric

Optic

Defines the minimum particle size you are able to detect. Electronicalbackground noise due to scattered light from gas moleculesor particle scattering

Defines themaximum particlesize you areable to detect

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physical background: single particle light

scattering, scattering intensity polar diagram

[Baron & Willeke, 2001, Haller 1999]

BACKWARD

SCATTERED

Scattered intensity I is a

function of

α = size parameter = π dp/λwith dp= particle diameter,

λ = incident wavelength

m = refractive index = n -iwith n = real part (scattering),

i = imaginary part (absorption)

Θ = scattering angle 0°-180°while ~0° = backward scattered,

~180° = forward scattered

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scattering, scattering intensity 3D plot

calculation of the scattering intensity

for a spherical particle, dp = 2µm, incident light: laser, λλλλ = 633nm

Figure from: René Michels, ILM Uni-Ulm

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principles of optical particle detection:

components, function and design

component function/designSample air inlet reproducibility, rH, isokinetic / various

Sample air pump flow rate, concentration, statistic / various

Light source signal / laser, diode laser, white light

well defined optical volume / various Beam optic

Light trap avoiding noise / various

Detection opticknown aperture / backward, forward, 90°

optical or aerodynamic focusing

Detector scattering light / photo diode, multiplier

Signal processing

& data processing rapid count processing and

accurate size classification / various

All components together determine the spectrometersAll components together determine the spectrometers

counting efficiency (coincidence concentration)counting efficiency (coincidence concentration)

and sizing accuracy (particle size resolution) and sizing accuracy (particle size resolution)

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principles of particle detection

Nephelometer

x

y

y

aerosol particles

detection volume

Signal by a

groupgroup of particles!

Light source

Detector

Sample in

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principles of particle detection

Spectrometer e.g. 90° detection

y

90°

x

yz

aerosol particlesaerosol focusing

detection volume

Signal by a

singlesingle particle!

Light source

Detector

Sample in

Light trap

GRIMM can do!! GRIMM can do!! 14



scattering, Grimm spectrometer principle

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principles of particle detection Dual method,

spectrometer and gravimetric filter (Grimm)

Light scattering in real time for

particle number concentration and

size distribution

Particle sampling on filter for

gravimetric use to determine

specific particle mass

(1) filter chamber, open

with 49mm PTFE filter (2)

Dual technology

in one device!

Grimm patent!

aerosol focusingaerosol focusing

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TSP

WRAC

(Wilson and Suh, 1996)

Particle Size in (µm)

TSP

Hi-vol

PM10PM2.5

Mass/ lo

g D

(µg

3/m

3)

PM1

GRIMM AEROSOL SPECTROMETER RANGE

DIFFUSION SEDIMENTATION

physical background: particle mass and

particle size fractions

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specification: grimm spectrometer

Specifications

Dust range [µg/m³]

Size Range [µm]

Size channels [µm]

#1.108

0.1…>100 000

0.3…>20

15 channels counts

16 channels mass (0.23)/0.3/0.4/0.5/0.65/

0.8/1/1.6/2/3/4/5/7.5/10/

15/20

#1.109

0.1…>100 000

0.25…>32

31 channels counts

32 channels mass (0.23)/0.25/0.28/0.3/0.35/0.4/0.45/

0.5/0.58/0.65/0.7/0.8/1/1.3/1.6/2/

2.5/3/3.5/4/5/6.5/7.5/8.5/10/12.5/

15/17.5/20/25/30/321.2 l/min

up to 2 000 000 P/l

up to 8h

2.5 kg with battery / 24 x 12 x 6 cm

Sample air

Particle counting

Battery duration

Weight / Dimensions

Particle concentration in particles/litre, for all size channels

or Particle mass in µg/m³, for all size channels

Particle mass fractions in µg/m³, simultaneously according

to EN 481 occupational (inhalable, thoracic, respirable) and

EPA environmental (PM10, PM2.5, PM1)

Data output

via Windows®

software

grimm aerosol spectrometer and dust monitors measuring … · 2014-07-28 · 1 1 wolfgang...

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