ELPI®+ (Electrical Low Pressure Impactor) is an improved version of the widely used and well characterized ELPI® -system. ELPI®+ enables measurement of real-time particle size distribution and concentration in the size range of 6 nm – 10 μm with 10 Hz sampling rate. The ELPI®+ features include real-time stand-alone operation, wide sample concentration range, wide particle size range and robust structure for operation even in harsh conditions. In addition to gaining real-time particle size distribution data, the ELPI®+ can be used for real-time particle charge distribution and for gravimetric impactor measurements. The use of impactor technology also enables post-measurement chemical analysis of size classified particles. All these features make the ELPI®+ and ideal choice in wide range of particle measurement applications including combustion aerosol and engine exhaust studies, pharmaceutical inhaler development, air quality monitoring and general aerosol research.


ELPI®+  features include

  • Wide particle size range; 6 nm – 10 μm
  • 14 particle size fractions, 500 with HR-ELPI®+
  • 10 Hz sampling rate
  • Possibility to collect size classified particles for chemical analysis
  • Wide operational concentration range
  • Independent stand-alone operation or control via laptop using ELPI®+VI software
  • Large 7" WVGA display with graphic user interface
  • Analogue inputs and outputs

Upgrade to advanced ELPI®+ versions

Most existing ELPI®+ units can easily be upgraded to High Resolution and High Temperature ELPI®+ versions without need for return to Dekati or local service center.

The wide measurement range of 6 nm – 10 µm makes ELPI®+ suitable for wide range of particle measurement applications. Due to its rapid time response, ELPI®+ is an ideal tool for studying unstable concentrations and size distributions, and evolution of size distributions. The standalone operation makes ELPI®+   suitable also for long term monitoring of e.g. air quality. In addition, ELPI®+ has an automatic feature for measuring particle charge size distributions suitable for characterizing e.g. efficiencies of electrostatic precipitators (ESP) and pharmaceutical aerosols.
The low pressure impactor used in the ELPI®+ is a robust stainless steel detector that can be applied even to rough environments, and the use of impactor technology enables post-measurement chemical analyses of the size fractionated samples in the range of 16 nm – 10 µm. Typical ELPI®+ applications include:

Example data on ELPI®+ display

Together with Dekati® Sample Conditioning instruments, Dekati is able to provide complete measurement solutions for many different types of particle measurement applications.

Particle size range                                      
0.006 – 10 µm               
Number of size classes 14, up to 500 with HR-ELPI®+
Sample flow rate 10 lpm
ELPI®+ dimensions H 407 x W 454 x D 242 mm
Collection plate diameter 25 mm
Unit weight 22 kg
Pump requirements* 20 m3/h at 40 mbar
Operating temperature 10 – 35 ºC, sample temperatures up to 180 °C with HT-ELPI®+
Operating humidity 0 – 90 % RH Non-condensing
Power 100 – 250 V, 50 – 60 Hz, 200 W
Sampling rate 10 Hz
Connection to PC (optional) RS-232 or Ethernet
6 analogue inputs 0 – 5 V
3 analogue outputs 0 – 10 V

Computer requirements

MS-Windows 7™, 8™ or 10™  














*Suitable pumps available at Dekati Ltd.


Impactor cutpoints

 15  10  
 14  5.3  7.3
 13  3.6  4.4
 12  2.5  3.0
 11  1.6  2.0
 10  0.94  1.2
 9  0.60  0.75
 8  0.38  0.48
 7  0.25  0.31
 6  0.15  0.19
 5  0.094  0.12
 4  0.054  0.071
 3  0.030  0.040
 2  0.016  0.022
 1  0.006  0.010     















Each ELPI®+ unit is individually calibrated before delivery; the calibration includes detailed determination of the exact sample flow rate and D50% values. The nominal values are presented in the table above.





The ELPI®+ operating principle can be divided into three major parts; particle charging in a unipolar corona charger, size classification in a cascade impactor and electrical detection with sensitive electrometers. The particles are first charged into a known charge level in the corona charger. After charging, the particles enter a cascade low pressure impactor with electrically insulated collection stages. The particles are collected in the different impactor stages depending on their aerodynamic diameter, and the electric charge carried by particles into each impactor stage is measured in real-time by sensitive electrometers. This measured current signal is directly proportional to particle number concentration and size, thus the ELPI®+ gives particle concentration and size distribution in real-time. By switching the charger unit off, the ELPI®+ can be used for particle charge distribution measurements.



All the components in the ELPI®+ are housed in a single compact unit. The instrument can be controlled and the measured data monitored in real-time on the 7” WVGA display in the ELPI®+ front panel or the ELPI®+VI™ software installed on an external laptop or PC. Data can either be saved a USB drive in the ELPI®+ unit, network drive or the external laptop and analysed further using the ELPI®+ data processing spread sheet provided with the ELPI®+. The unit also includes 6 analogue inputs and 3 outputs as a standard. In addition, two K-type thermoelement signals can be logged into the unit. All data is saved into one data file for easy post-processing.



Keskinen, J., Pietarinen, K. and Lehtimäki, M. (1992) Electrical Low Pressure Impactor, J. Aerosol Sci. 23, 353-360. 

Järvinen, A., Aitomaa, M., Rostedt, A., Keskinen, J. & Yli-Ojanperä, J. 2014. Calibration of the new electrical low pressure impactor (ELPI+). 2014 J. Aerosol Sci. 69, pp. 150-159.

Virtanen, A., Marjamäki, M., Ristimäki, J., Keskinen, J. (2001). Fine particle losses in electrical low-pressure impactor, Journal of Aerosol Science, vol 32, pp 389-401. 

Marjamäki, M. 2003. Electrical Low Pressure Impactor: Modifications and Particle Collection Characteristics. PhD thesis. Tampere University of Technology Publications 449.



Spare Impactor + Charger Unit

Easily replaceable spare impactor and charger units are available as accessories for ELPI®+. The spare impactor and charger unit can be used in the ELPI®+ while the other impactor and charger unit is being serviced. This enables making continuous ELPI®+ measurements even during service breaks. A spare collection plate sets are also available as accessories.


Collection substrates

Different types of collection substrates can be used on the ELPI®+ impactor collection plates. Even though gravimetric or chemical analyses are not made, collection substrates are recommended to be used to prevent fouling of the impactor. The collection plates are designed for 25 mm substrates and Dekati offers aluminium and polycarbonate substrates for this purpose. For the suitability of different types of substrates, please contact support@dekati.fi.


Dekati® Collection Substrate Spray

The collection substrates are often greased in impactor measurements to prevent particle bounce and blow-off from the impactor stages. The Dekati® Collection Substrate Spray is developed to grease the substrates faster and more evenly than with the traditional greasing methods. When used together with a stencil, the Dekati® Collection Substrate Spray enables an easy and fast way of applying a thin and smooth layer of grease on the collection substrates. The grease used in the spray is non-volatile also at low pressures and is therefore suitable for use in low pressure impactors, and also chemically pure enough to enable most chemical analysis to be done from the substrates. Stencils are available for 25 mm substrates that are used in the ELPI®+, High Resolution ELPI®+, High Temperature ELPI®+, ELPI®, DLPI+, DLPI and Dekati® PM10 impactors.


Sintered collection plate set

Sintered collection plates are designed to prevent common problems in impactor measurements: impactor overloading and particle bounce. Instead of collecting the particles on a smooth aluminium foil the collection area is vacuum oil embedded porous metal. When the particles are collected on this oily porous metal surface, the oils seeps up due to capillary forces and thus the impaction always occurs to a liquid surface effectively eliminating bouncing.

The sintered collection plates are specially designed for measurements where the particles are particularly solid and bouncy, such as salt or diesel soot after removal of volatile hydrocarbons. The use of sintered collection plates allows the user to collect up to 10 or 20 times more particle material when compared to normal collection plates without affecting the measured data.


Dekati® Dryer

Since ELPI®+ standard setup measures particles in real-time without any sample conditioning, it detects the particles as they are in ambient air and the measured particle size can be slightly different from the result measured with other methods that use a heated sampling line, dilution or particle dryer before the actual particle detection. This difference is caused by water absorbed by the particles which increases the particle size and mass especially in high humidity environments. The Dekati® Dryer DD-600 is a Nafion dryer used to remove water from the aerosol before it enters the ELPI®+ and it is specially designed for particle measurements and calibrated for particles. The Dekati® Dryer Setup DD-603 includes the Dekati® Dryer, PM10 inlet and all necessary connections for a complete setup in air quality measurements. In this setup, the drying air for the Dekati® Dryer can be supplied from the same vacuum pump that is used to operate the ELPI®+ unit so no additional source for drying media is required.


Other accessories for ELPI®+ include

Vacuum pumps  
DP25 230V/50 Hz, EUR IA-904
DP25 100V/50 Hz, JPN IA-905
DP25, 115V/60 Hz, USA IA-906
ELPI®+ upgrade options  
High Resolution ELPI®+ HR-ELPI+
High Temperature ELPI®+ HT-ELPI+
Sample conditioning and dilution  
Dekati® Cyclone for separtaion of >10 µm particles SAC-65
Sampling nozzles for isokinetic sampling SAC-100
Dekati® Diluter for aerosol dilution DI-1000
FPS-4000 for emission dilution FPS-4000
DEED Dekati® Engine Exhaust Diluter DEED-100
Dekati® Axial Diluter DAD-100

For more accessories, please contact Dekati Ltd.

ELPI®+ brochure

Available in customer pages section:

ELPI®+ Manual
ELPI®+VI Manual
Data processing spread sheet
Spare part catalogue


Maintenance videos available in Youtube.

Can’t find what you’re looking for?
Contact Dekati technical support: support (at) dekati.fi
Contact Dekati sales: sales (at) dekati.fi


To use a PDF document, a reader program must be installed on your computer to display, print, and navigate. The Adobe Acrobat reader is available for downloading at no cost from Adobe's Web site at http://www.adobe.com [http://www.adobe.com]. To ensure you will be able to see a PDF file in its entirety, please obtain the most recent edition of the free Acrobat Reader.



Related products:
High Resolution ELPI®+
High Temperature ELPI®+