miniDiSC

This page is really old!

The miniature diffusion classifier (or miniDiSC for short) that is described on this page was developed in 2008. We built about 30 of these devices at The University of Applied Sciences Northwestern Switzerland, and then handed it over to an industry partner (Matter Engineering) in 2010 who sold it commercially as "DiSCmini". Matter Engineering was later acquired by Testo, who continued selling this device until recently. In the meantime, I have co-founded another company that makes handheld nanoparticle detectors, and unsurprisingly, another 15 years of development have resulted in newer and better designs, most notably the Partector 2 and the Partector 2 Pro, which you can find on the webpage of naneos.

I am leaving this page up, but more as a historical reference. Everything written below is old, and referred to the DiSCmini at the time of its creation around the year 2010, and is no longer current.

Latest news

  • 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 sales-nanoparticle@testo.de .

Overview

The 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.

Specifications

The 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.

Applications

The 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
In most cases, a quick measurement with a miniDiSC will answer the question whether or not there is an air quality problem in a given area.

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.

Accessories

The 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 Contact

The 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 Software

You 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.

MiniDiSC factsheet

MiniDiSC presentation

MiniDiSC quick start guide

MiniDiSC manual

MiniDiSC Excel addIn manual

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.

References

The 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.