Instrument for the measurement of airborne particle size distribution in real-time

The ELPI®+ (Electrical Low Pressure Impactor) is a real-time particle measurement instrument for measuring airborne particle size distribution in real-time. The operating principle is based on well-known ELPI® technology. The particles are first charged into a known charge level in a corona charger. After charging, the particles are size classified in a low-pressure cascade impactor according to their aerodynamic particle size. The impactor stages are electrically insulated and connected to sensitive electrometers at each impactor stage. The charged particles collected in a specific impactor stage produce an electrical current, which is recorded by the respective electrometer channel. This current is directly proportional to the number concentration of particles on that stage. The electrometers’ readouts are recorded and processed in the onboard computer/controller unit (MS Windows® platform) equipped with internal long-term memory storage, as well as wide range of connectivity devices (USB, RS-232 serial and Ethernet). The device can be programmed for standalone operation with automatic sampling cycle, as well as remote controlled and monitored (including live data feed).

The ELPI®+ measures particles in 14 size fractions in the range from 6 nm to 10 μm. The 13 impactor stages operating in the range of 16 nm - 10 μm collect the sample on a foil/filter that can be analyzed after the real-time measurement to get chemical composition of particles in each particle size class. The final stage measuring real-time particle concentration in the range of 6 nm - 16 nm is a back-up filter stage.

The device is routinely used in research covering the problematics of airborne tribo-emissions related to dry friction, e.g. in friction brake systems.

Dekati ELPI+, general view 

Dekati®ELPI®+, coupled with RTEC MFT-5000 tribometer (pin – on – disc configuration)

Dekati ELPI+, schematic, main components and principle of operation 

Nominal specifications of the impactor

Stage

D50%

[µm]

Di [µm]

Number min

[1/cm3]

Number max

[1/cm3]

Mass min

[µg/m3]

Mass

max

[mg/m3]

14

5.3

7.3

0.10

1.7E+04

11

3400

13

3.6

4.4

0.10

3.0E+04

4

1300

12

2.5

3.0

0.16

5.2E+04

2.3

730

11

1.6

2.0

0.3

9.7E+04

1.3

400

10

0.94

1.2

0.6

2.0E+05

0.6

195

9

0.60

0.75

1.2

3.9E+05

0.3

85

8

0.38

0.48

2

6.8E+05

0.12

38

7

0.25

0.31

4

1.2E+06

0.06

17

6

0.15

0.19

6

2.0E+06

0.03

7.7

5

0.094

0.12

12

3.7E+06

0.01

3.2

4

0.054

0.071

21

7.0E+06

0.004

1.3

3

0.030

0.040

42

1.4E+07

0.0015

0.47

2

0.016

0.022

90

3.0E+07

0.0005

0.16

1

0.006

0.010

240

7.9E+07

0.0002

0.03

Basic operational parameters 
  • Nominal air flow: 10 l/m
  • Particle size range: 0.006 − 10 µm
  • Number of channels: 14 electrically detected + pre-separator stage. Up to 500 chann. available with High Res. ELPI®+
  • Sampling rate: 10 Hz
  • Analog channels: 3 analog outputs 0 − 10 V, 6 analog inputs  0 − 5 V
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