- We are continuing to develop our instrument designs, and have just recently developed the world's smallest nanoparticle detector with many technical improvements over the miniDiSC described here - see www.naneos.ch.
- A software update to version 1.2. of the java tool now also allows calculation of UFP total (not lung-deposited) surface area and mass concentration. Please note that this calculation relies even more on the assumed shape of the particle size distribution than other calculations, and thus is at best a reasonable estimate, to be taken with a large grain of salt.
- Our paper on the miniDiSC in the journal of aerosol science and technology is now freely accessible (M.Fierz, C.Houle, P.Steigmeier and H.Burtscher, Aerosol Science and Technology 45:1-10, 2011)
- A recent study (C.Asbach et al., Annals of Occupational Hygiene 56:606-621, 2012) tested several handheld nanoparticle monitors, among others the miniDiSC - apparently, it did well! Comparability of Portable Nanoparticle Exposure Monitors
- Another recent paper (R.Meier, K.Clark and M.Riediker, Aerosol Science and Technology 47:22-28, 2013) compared the miniDiSC with the TSI p-Trak handheld CPC and with an SMPS, and concluded that the miniDiSC did better than the p-Trak, and well enough to be a useful tool for personal exposure measurement in traffic-influenced sites. Comparative Testing of a Miniature Diffusion Size Classifier to Assess Airborne Ultrafine Particles Under Field Conditions
- The miniDiSC is now available commercially from Testo! They have changed the name to DiSCmini, and the instrument looks slightly different from the outside, but otherwise it is identical to the version described here. For inquiries, please contact firstname.lastname@example.org .
OverviewThe miniature diffusion size classifier (or miniDiSC for short) is a new instrument for nanoparticle measurement. It was designed with ease of use in mind - it is truly handheld, operates without working fluids or radioactive sources, operates in any orientation and on-the-go. It can be used for personal exposure monitoring or quick walk-through surveys of an area of interest, such as a workplace, or an urban area with heavy traffic. Its concentration detection limit is ideally suited for typical ambient particle concentrations. The miniDiSC is less accurate than traditional aerosol instruments such as CPC (condensation particle counter) and SMPS (scanning mobility particle sizer), available from e.g. TSI or Grimm, but this is often more than compensated for by its smaller size and easier handling. In general, measured concentrations and average diameters agree to within 30% with CPC and SMPS (more details are available in the application note #11). Compared to its main competitor (the handheld CPC) it is smaller, easier to use and also delivers an average particle diameter and lung-deposited surface area and not only the particle number concentration. The handheld CPC is better suited when only number concentration is of interest, and when particle concentrations are below 1'000 per ccm.
SpecificationsThe miniDiSC uses a patented technique to determine the particle number concentration as well as the average particle diameter of the aerosol with purely electrical means - particles are charged in a unipolar diffusion charger and then detected in two electrometer stages. Additionally, the instrument is calibrated to report the lung-deposited surface area just like the TSI Nanoparticle Surface Area Monitor. The internal charger can be turned off, and the miniDiSC will then operate as the world's smallest aerosol electrometer. The miniDiSC has a time resolution of 1 second.
The miniDiSC runs on an internal rechargeable Li-ion battery with a lifetime of approximately 8 hours. It stores its raw data on an SD-card; raw data files can be imported directly into Excel with an import macro, or analyzed with a cross-platform Java tool.
The miniDiSC measures 180x90x45mm and weighs 700g. It is one of the smallest instruments capable of nanoparticle measurement available today. For more details on its performance, please follow the links in the literature section below.
ApplicationsThe miniDiSC is ideally suited for all measurements where accuracy is not quite as important as ease of use. Its number concentration range is approximately 1'000 - 1'000'000 particles/ccm, which covers typical ambient particle levels (but not clean-room particle levels). We can customize it with less sensitive electrometers to measure higher particle concentrations if necessary, such as can occur in workplace settings. The miniDiSC can only size particles smaller than about half a micron correctly, and is thus not suited for microparticles. Typical applications of the miniDiSC are
- Personal exposure monitoring
- Workplace hazard identification
- Filtration efficiency verification
- Air pollution mapping with one mobile or multiple stationary instruments
Due to its small size and low weight, the miniDiSC can also be used easily for airborne measurements, e.g. with a balloon or small Zeppelin. It was recently selected for an overflight of the Kilimanjaro by researchers of the University of Fribourg.
AccessoriesThe miniDiSC is shipped in a rugged protective housing, which contains the instrument and the charger for the internal battery. For use in the field, it comes with a protective neoprene sleeve (visible in the Kilimanjaro image above), equipped with a belt clip so that it can be carried on a person's belt. There is an inlet impactor with a cutoff diameter of ~0.7 micron to remove coarser particles which the miniDiSC cannot size properly. Software for data analysis is also included (see below).
Team and ContactThe miniDiSC was developed jointly by Martin Fierz, Peter Steigmeier and Corey Houle in professor Heinz Burtscher's group at the University of Applied Sciences Northwestern Switzerland, Windisch, Switzerland. If you are interested in trying or buying a miniDiSC, or if you would like more information than what you can find on this site, please contact Martin Fierz at [martin dot fierz at fhnw dot ch].
Literature and SoftwareYou can download product factsheets, application notes, the manual and the quick start guide here. Furthermore, you can download the Excel-add-in to import miniDiSC data into Excel with a single mouse click. Finally, you can launch the cross-platform Java data analysis software directly here. All material below except the Java tool is © 2010 FHNW.
Application note #1: Standard operating procedures
Application note #2: Warnings on the instrument
Application note #3: Warnings in the Java tool
Application note #4: On measured and calculated values
Application note #5: On different inlet options
Application note #6: Corona wire contamination by silicon oxide
Application note #7: Cleaning the corona wire
Application note #8: On lung-deposited and active surface area
Application note #9: On mass and total surface area calculation
Application note #10: Resetting the miniDiSC calibration if it is lost
Application note #11: Errors due to the size distribution shape
Excel add-In for 3.20 firmware and later. This add-in is deprecated! You should use the java tool instead. The java tool calculates more exactly, and checks the status of the instrument as seen in the data file, and will warn you if something is wrong; this is very important for quality assurance!
Launch the java tool, © Martin Fierz
A sample data file which you can use with the Excel-addIn (for firmware 3.20 and later) and the Java tool (right-click the data file link and choose save as... from context menu to save it to your PC, then open it with the Java tool). The data file comes from a bike ride from ETH Zürich to my home.
New! You can combine your miniDiSC data with GPS data in the standard gpx file format to produce a Google Earth track with just a few mouseclicks in the Java tool! The examples on the right show a bike ride around our university and the beginning of my trip home from the 2010 international aerosol conference in Helsinki. Download the Google Earth file - obviously you need to have Google Earth installed to view it.
ReferencesThe miniDiSC and similar technology developed in our lab have been the subject of a number of publications. Due to copyright restrictions I cannot offer them for download here; if you cannot access them because your institution doesn't have a subscription to these journals, I can send them by mail on request.
- M. Fierz, P. Steigmeier, C. Houle and H. Burtscher: Design, Calibration and Field Performance of a Miniature Diffusion Size Classifier, Aerosol Science and Technology, 45, 1-10 (2011).
- M. Fierz, A. Keller and H. Burtscher: Charge-based personal aerosol samplers, Inhalation Toxicology, 21, s1 30-34 (2009).
- M. Fierz, S. Weimer and H. Burtscher: Design and performance of an optimized electrical diffusion battery, Journal of Aerosol Science, 40 152-163 (2009).,
- M. Fierz, H. Burtscher, P. Steigmeier and M. Kasper: "Field measurement of particle size and number concentration with the Diffusion Size Classifier (DiSC)", SAE 2008-01-1179
- M. Fierz, L. Scherrer, and H. Burtscher: Real-time measurement of aerosol size distributions with an electrical diffusion battery, J. Aerosol Sci. 33 (7), 1049-1060 (2002),