Grimm Aerosol Technik GmbH & Co. KG

2016 1

The MINI-WRAS

Dipl. Ing. (FH) Andreas Jaksch

GRIMM`s proven High-Tech Dust Monitoring

Grimm Aerosol Technik GmbH & Co. KG

2016 4

Measurement principle Mini-WRAS

Physical principle(s) of operation electrical mobility plus optical light scattering (single particle counter) 1: Aerosol Spectrometer Measuring cell with light generator and receiver module 2: NanoSizer Unipolar diffusion charger with time multiplexed electrode and faraday cup electrometer Measured physical quantities primary particle size distribution, total number concentration secondary surface and volume distribution, total surface and total volume mass fractions: PM10, PM2,5, PM1 and inhalable, thoracic, alveolic

Grimm Aerosol Technik GmbH & Co. KG

2016 5

Optical Particle Detection Method

Grimm optical cell • Light source by compact laser diode with multiplex mode, low power consumption and good temperature stability • Collimator generates laser curtain with homogeneous optical field • Light trap assures low noise due to very low indirect scattering light • Inlet focus particles aerodynamically into optical field, no border zone error • Rinsing air circuit and outlet nozzle design assure straight pass through the laser, no vagabonding particles • Fast and robust photo diode detector for 90° scattering light detection • Special wide field reflector improves detection limit for small particles and reduces sizing effects by refractive index • 31 size channels, 6 sec. time resolution, PM10, 2.5,1, thoracic, E- and A-fraction

Grimm Aerosol Technik GmbH & Co. KG

2016 6

Size range 0,25 – 32 µm in 31 size channels

0,25 µm 32 µm

Laser Aerosol Spectrometer particle sizing

Grimm Aerosol Technik GmbH & Co. KG

2016 7

The optical particle counter measures the size distribution from 250 nm to 32 µm in 31 size channels. The intensity of the scattered light is used for the determination of the particle size (single particle counting). For each size channel the particle number is measured. Therefore the volume flow (1.2 l/min) is controlled with the pressure drop at an orifice. Under the estimation of spherical particles the mass distribution will be calculated. The mass distribution is subsequently converted into the fractions PM10, PM2.5, PM1 and also Inhalable, Thoracic and Alveolic.

Aerosol Spectrometer

Grimm Aerosol Technik GmbH & Co. KG

2016 8

The electrical sensor consists of 3 main elements: a unipolar electrical diffusion charger a time multiplexed electrode (deposition of particles) and a faraday cup electrometer

NanoSizer

Grimm Aerosol Technik GmbH & Co. KG

2016 9

Unipolar diffusion charger

The gas ions produced by the corona are accelerated towards a grid.

The grid voltage allows a small amount of ions to pass the grid. The

ions move towards the surrounding concentric ground electrode, where

some of them diffuse onto particles and charge them.

gas ions

GND

inlet aerosol particle

corona high voltage

grid

Grimm Aerosol Technik GmbH & Co. KG

2016 10

Multiplexed electrode

The charged aerosols enter a section, consisting of a round-shaped outer

wall which is at electrical potential (GND) and a concentric conductivity

electrode which operates at different voltages:

The higher the voltage is the more particles are removed, depending on

their electrical mobility.

Grimm Aerosol Technik GmbH & Co. KG

2016 11

Multiplexed electrode

The deposition of the particles at the multiplexed electrode is a function of

the particle diameter, the charge of the particle, the aerosol flow, the

electrode´s diameter and length and of the electrode voltage.

By changing the voltage, a certain amount of particles is extracted from the

aerosol flow. The higher the electrical mobility of the particles (smaller

diameter or higher charged) is, the higher is the amount of particles that will

deposit on the outer electrode.

Only particles with an electrical mobility less than a certain limit value will

pass the electrode and are measured with a Faraday cup electrometer.

Grimm Aerosol Technik GmbH & Co. KG

2016 12

The NanoSizer measures 10 different currents (one each 6 seconds) that results in a total scan time of 1 minute. The voltage of the electrode can be changed from 2 V to 320 V. With these 10 currents it is possible to determine the particle number concentrations for 10 size channels. At the beginning of a measurement a zero scan is done to measure the offset current.

GRIMM NanoSizer

Grimm Aerosol Technik GmbH & Co. KG

2016 14

• Size range: 10 nm to 32 µm • Size resolution: 41 size channels • Time resolution: 60 seconds for a complete scan • No consumables • Full remote control via Bluetooth • Battery operation (> 8 h) • stand alone and portable device • easy to use (with and without tablet or PC)

Main features Mini-WRAS

Grimm Aerosol Technik GmbH & Co. KG

2016 16

Online overview

All information is available at a glance

Grimm Aerosol Technik GmbH & Co. KG

2016 17

Counts

Grimm Aerosol Technik GmbH & Co. KG

2016 18

Particle mass distribution

Grimm Aerosol Technik GmbH & Co. KG

2016 20

Calibration of the Nanosizer

Reference SMPS GRIMM Mini-WRAS

Setup

The NanoSsizer is calibrated with monodisperse aerosol (NaCl) against the reference SMPS

Grimm Aerosol Technik GmbH & Co. KG

2016 22

The new GRIMM Mini-WRAS is a combination of the GRIMM NanoSizer and an aerosol spectrometer.

It measures particles from 10 nm to 32 µm in 41 size channels.

The minimum time resolution of one scan is only 60 s.

The system is light, compact and does not need butanol or a radioactive source (in comparison to SMPS + CPC).

Conclusions