miniDiSC

The miniDiSC is now available commercially from Matter Aerosol! 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.

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. 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

Excel add-In for 3.20 firmware and later (add-In for earlier firmware versions available on request).

Launch the java tool (demo), © 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.