Embed Size (px)
Citation preview
[email protected] ETH 2009 1
Miniature diffusion sizeclassifiers for personal monitoring and sensor networks
M.Fierz, C. Houle, P. Steigmeier and H. Burtscher
Fachhochschule Nordwestschweiz, Windisch, Switzerland
[email protected] ETH 2009 2
The diffusion size classifier (DiSC)
Particles are labelled with positive chargesin a unipolar charger, so that they can laterbe detected by the current they induceParticles are deposited by diffusion in a "diffusion stage" and detected as an electrical currentRemaining particles end up in a filter stage
detectable current
[email protected] ETH 2009 3
DiSC (2)Diffusional deposition is size-selective: smaller particles are captured moreefficientlyFilter stage current divided by diffusionstage current => particle sizeTotal current + particle size => particlenumber
[email protected] ETH 2009 4
DiSC vs DC (Diffusion Charger)
charger Diff.Stage PumpFilter
StageDiffusion Size Classifier(DiSC)
charger PumpFilter Stage Diffusion Charger
(DC)
average particle size,particle number
no size/number informationmeasures „diameter concentration“Can be interpreted as lung depositedsurface area – interesting!?
[email protected] ETH 2009 5
2008 Personal Monitor Prototype (DC)
770 grams9h battery life45x82x180mmData stored on SD-card
10x smaller and lighter than existingdiffusion charging instruments
[email protected] ETH 2009 6
Personal Monitor 2009
670 grams8h battery life40x90x180 mmData stored on SD-cardUSB connection to PC
It's DiSC instead of DC(but it could be a DC too)
[email protected] ETH 2009 7
Personal Monitor 2009DiSC measures particle numberaverage diameter and DC signalwith a time resolution of 1 secondDetection limits:~10…200nm (DC: no upper limit)~1e3…1e6 pt/ccmAccuracy typ. +-30%
12 times smaller thanthe original DiSC
[email protected] ETH 2009 8
No free lunch…
a lower flow rate (1lpm) = lower signals = higher detection limitsa weaker pump (less underpressure possible)finer meshes in the diffusion stage whichrequire more frequent cleaning & recalibrationLess power available for heating to stabilizetemperature
Compared to the desktop DiSC, the miniDiSC has
[email protected] ETH 2009 9
Intermediate conclusion
We can build both a DiSC and a DC in a miniature packageBoth instruments seem interesting to meThe DiSC is a „superset“ of the DC –you get DC signal plus particle numberplus average particle diameter
[email protected] ETH 2009 10
Application 1: Personal exposure
Two distinct applications:Useful in occupational hygiene, whereexposed persons can be warned instantlyUseful in medical studies, because a directlink between exposure and effect isestablished
[email protected] ETH 2009 11
Application 2: portable „PMP“
1:16 (?) dilution
200°C (?)
Particle lossesin ion trap:
[email protected] ETH 2009 12
Application 3: Monitoring network
6 miniDiSCs were deployed for one week in ZürichEnvironmental enclosures used in exposedlocations220V mains power usedExternal battery packin enclosure would lastapproximately one weekData recorded to SD-card
[email protected] ETH 2009 13
Results
ETH
Totally different type of data thanthat available today –high temporal and potentially high spatial resolution
[email protected] ETH 2009 14
Wireless monitoring network
http://147.86.20.28/minidisc.html(limited time only!)
[email protected] ETH 2009 15
SummaryThe miniDiSC is a new handheld aerosoldetectorDiSC or DC?It should useful both for exposure studiesas well as for flexible measurementnetworks, such as transport of PM from a localized source(not for long-term-monitoring!)It might be useful for „PMP-like“ fieldmeasurements in combination with a simple thermodiluter
[email protected] ETH 2009 16
Acknowledgements
WorkCorey Houle (mechanical design) Peter Steigmeier (electronics)
Monitoring Network ExampleSusanne Schlatter (UGZ)Peter Mertes (PSI)
FundingForschungsfonds Aargau
