GRIMM Aerosol Spectrometer and Dust Monitors Measuring … · 2014-07-28 · 1 1 Wolfgang...
Transcript of GRIMM Aerosol Spectrometer and Dust Monitors Measuring … · 2014-07-28 · 1 1 Wolfgang...
1
1
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
2
Wolfgang Brunnhuber , Dr. Friedhelm Schneider
Part A
physical background
general principles of optical particle detection
Part B
Nanoparticles
counting and sizing
Agenda
3
Wolfgang Brunnhuber , Dr. Friedhelm Schneider
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
4
Wolfgang Brunnhuber , Dr. Friedhelm Schneider
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.
5
Wolfgang Brunnhuber , Dr. Friedhelm Schneider
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
6
Wolfgang Brunnhuber , Dr. Friedhelm Schneider
physical background: dependency of
particle size and wavelength on scattering
[Baron & Willeke, 2001]
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)
αααα = ππππ dp/λλλλ with dp= particle diameter; and λλλλ incident wavelength
note: ππππ dp = particle circumference, for spherical particles
Gustav Adolf Feodor Wilhelm Ludwig Mie
* 1868 † 1957
2
7
Wolfgang Brunnhuber , Dr. Friedhelm Schneider
physical background: dependency of
particle size and wavelength on scattering
[Baron & Willeke, 2001]
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!
αααα = ππππ dp/λλλλ with dp= particle diameter; and λλλλ incident wavelength
note: ππππ dp = particle circumference, for spherical particles
8
Wolfgang Brunnhuber , Dr. Friedhelm Schneider
physical background:
scattering intensity vs. particle size
[Baron & Willeke, 2001]
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
9
Wolfgang Brunnhuber , Dr. Friedhelm Schneider
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
10
Wolfgang Brunnhuber , Dr. Friedhelm Schneider
physical background: single particle light
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
11
Wolfgang Brunnhuber , Dr. Friedhelm Schneider
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)
12
Wolfgang Brunnhuber , Dr. Friedhelm Schneider
principles of particle detection
Nephelometer
x
y
y
aerosol particles
detection volume
Signal by a
groupgroup of particles!
Light source
Detector
Sample in
3
13
Wolfgang Brunnhuber , Dr. Friedhelm Schneider
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
Wolfgang Brunnhuber , Dr. Friedhelm Schneider
physical background: single particle light
scattering, Grimm spectrometer principle
15
Wolfgang Brunnhuber , Dr. Friedhelm Schneider
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
16
Wolfgang Brunnhuber , Dr. Friedhelm Schneider
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
17
Wolfgang Brunnhuber , Dr. Friedhelm Schneider
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