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On-line mobility analyzer: Set-up and first measurements
J. Aerosol Sci., Vol. 26. Suppl 1, pp. $771-$772, 1995 Elsevier Science Ltd Printed in Great Britain 0021-8502/95 $9.50 + 0.00
Pergamon
ON-LINE MOBILITY ANALYZER: SET-UP AND FIRST MEASUREMENTS U. Sievert. H. O. Luck Department of Communication Engineering, Duisburg University, FRG Bismarckstr. 81, D-47048 Duisburg Introduction: A number of methods has been used to measure the electrical mobility. The common type is the differential mobility analyzer (DMA) and the modified systems (RDMA, SDMA), based on the DMA-principle. Most of these methods destroy the aerosol by separation and/or deposition. The combination of electrically controlled unipolar charging and mobility dependend acceleration of the charged particles in the direction of the aerosol flow is applied to determine the particel mobility. A destruction of the aerosol is thus circumvented.
Theory of operation: The experimental setup is shown in Fig.1. Most of the used modules are presented/1,2/. A nozzle builds a sheath air covered aerosol beam. An unipolar charger is able to produce a homogeneous space-charge density and downstream at the end of the tube the charged aerosol induces electrostatically chargees on the surface of an annular electrode, measurable as a small current/3/. For the on-line mobility measurement a new module was designed. This module creates a homogeneous electrical field parallel to the tube axis. In the inner part of the tube the electric potential increases downstream from zero (charger region) to about 10 kV at the annular electrode. The electrode builds the end of the homogeneous electrical field. So, the current amplifier at the electrode works on a potential of 10 kV (Fig. 1). The potential in the accelerator tube was calculated by Drftboom/4/. He showed, that a number of ring-like electrodes, feeded with constant voltage between neighbouring rings, produces a very homogeneous electrical field in the center of the tube (Fig. 2).
Charger Sheath air
Aerosol.
Annular electrode
\ ~
II
II
•
H Tt tt
I
i
=
tt
T~
i ~
Sheath air
l
:
Electr. field
$771
]
Aerosol .
$772
U. SIEVERTand H. O. Luck F o r the on-line m e a s u r e m e n t of the mobility distribution the aerosol b e a m gets a small charge-impulse with the duration Tc. This cylindrical space-charge cloud induces two impulses with reversed sign in the annular electrode (see fig.
~ot ~
-10kV
~
N
~
u
N
~
m
m
m
Z
N
1). Figure 3 shows two )ili!~i~i!~i~ii~i~ii~i~i~i~!~i~iii~!i~iiiii!il m e a s u r e m e n t s , o n e with and one without an external .......................:.............................................................................................................................................. electrical field in the accelerator tube respectively. It occurs a s h a p e changing and a m o v e m e n t c o m p a r e d with the original curve. A detail of the rising e d g e of the first impulse is shown in figure 4. T h r e e different e of simulated aerosol distributions result in different risings of the curve. In general the w h o l e information a b o u t the aerosol mobility is included in the s h a p e changing o f the curves. A n e w on-line principle for mobility m e a s u r e m e n t presented. T h e detailed theoretical description is in preparation.
Conclusion:
20
i
~ i
i
15 i/pA lo
i
r_s~'9~c,:~.O'
Wi~h etec-t:r', field
was
elec±r,
E=50E3 ----...~
/
FieLd
o.4!
0.2
o
o 1,4
:i:~::!:;! i: !!iiiii!!iiiiii:~ii~!:i!iiii!::;ii?:~~e r
1.6
1.8
:~to~;~ ~elo
I/sec 2
1,5~
~iiiimtltmmi~lutomi:: ~
1.56
"~/S~C
1,6
~ !ti i :i ,.: ~iiiii~
The work was performed as part of the Special Research Program (SFB 209). The.author would like to thank the German Science Foundation (DFG) for sponsoring the WORK. References: /1/ Bernigau N.G. (1989). Time varying charge levels as an alternative roach for aerosol concentration measurements, J. Aerosol Sci., 2,Q,8, 1091-1994. Sievert, U., Luck., H. (1993), Electically unipolar aerosol charger with large dynamic range, J. Aerosol Sci., Vol. 24, S1, p. 493-494. /3/Bernigau, N. (1990) Ein Beitrag zur elektrischen Bestimmung der Partikelanzahlkonzentration yon Aerosolen, Dissertation, Univ. Duisburg, Germany. /4/Dr0tboom, M. (1994), Entwicklung einer Anordnung zur Beschleunigung elektr, gel. Partikel in FluBrichtung eines schutzluftumhiillten Aerosolstrahles, Diplomarbeit, Univ. Duisburg, Germany.
~p
Pergamon
ON-LINE MOBILITY ANALYZER: SET-UP AND FIRST MEASUREMENTS U. Sievert. H. O. Luck Department of Communication Engineering, Duisburg University, FRG Bismarckstr. 81, D-47048 Duisburg Introduction: A number of methods has been used to measure the electrical mobility. The common type is the differential mobility analyzer (DMA) and the modified systems (RDMA, SDMA), based on the DMA-principle. Most of these methods destroy the aerosol by separation and/or deposition. The combination of electrically controlled unipolar charging and mobility dependend acceleration of the charged particles in the direction of the aerosol flow is applied to determine the particel mobility. A destruction of the aerosol is thus circumvented.
Theory of operation: The experimental setup is shown in Fig.1. Most of the used modules are presented/1,2/. A nozzle builds a sheath air covered aerosol beam. An unipolar charger is able to produce a homogeneous space-charge density and downstream at the end of the tube the charged aerosol induces electrostatically chargees on the surface of an annular electrode, measurable as a small current/3/. For the on-line mobility measurement a new module was designed. This module creates a homogeneous electrical field parallel to the tube axis. In the inner part of the tube the electric potential increases downstream from zero (charger region) to about 10 kV at the annular electrode. The electrode builds the end of the homogeneous electrical field. So, the current amplifier at the electrode works on a potential of 10 kV (Fig. 1). The potential in the accelerator tube was calculated by Drftboom/4/. He showed, that a number of ring-like electrodes, feeded with constant voltage between neighbouring rings, produces a very homogeneous electrical field in the center of the tube (Fig. 2).
Charger Sheath air
Aerosol.
Annular electrode
\ ~
II
II
•
H Tt tt
I
i
=
tt
T~
i ~
Sheath air
l
:
Electr. field
$771
]
Aerosol .
$772
U. SIEVERTand H. O. Luck F o r the on-line m e a s u r e m e n t of the mobility distribution the aerosol b e a m gets a small charge-impulse with the duration Tc. This cylindrical space-charge cloud induces two impulses with reversed sign in the annular electrode (see fig.
~ot ~
-10kV
~
N
~
u
N
~
m
m
m
Z
N
1). Figure 3 shows two )ili!~i~i!~i~ii~i~ii~i~i~i~!~i~iii~!i~iiiii!il m e a s u r e m e n t s , o n e with and one without an external .......................:.............................................................................................................................................. electrical field in the accelerator tube respectively. It occurs a s h a p e changing and a m o v e m e n t c o m p a r e d with the original curve. A detail of the rising e d g e of the first impulse is shown in figure 4. T h r e e different e of simulated aerosol distributions result in different risings of the curve. In general the w h o l e information a b o u t the aerosol mobility is included in the s h a p e changing o f the curves. A n e w on-line principle for mobility m e a s u r e m e n t presented. T h e detailed theoretical description is in preparation.
Conclusion:
20
i
~ i
i
15 i/pA lo
i
r_s~'9~c,:~.O'
Wi~h etec-t:r', field
was
elec±r,
E=50E3 ----...~
/
FieLd
o.4!
0.2
o
o 1,4
:i:~::!:;! i: !!iiiii!!iiiiii:~ii~!:i!iiii!::;ii?:~~e r
1.6
1.8
:~to~;~ ~elo
I/sec 2
1,5~
~iiiimtltmmi~lutomi:: ~
1.56
"~/S~C
1,6
~ !ti i :i ,.: ~iiiii~
The work was performed as part of the Special Research Program (SFB 209). The.author would like to thank the German Science Foundation (DFG) for sponsoring the WORK. References: /1/ Bernigau N.G. (1989). Time varying charge levels as an alternative roach for aerosol concentration measurements, J. Aerosol Sci., 2,Q,8, 1091-1994. Sievert, U., Luck., H. (1993), Electically unipolar aerosol charger with large dynamic range, J. Aerosol Sci., Vol. 24, S1, p. 493-494. /3/Bernigau, N. (1990) Ein Beitrag zur elektrischen Bestimmung der Partikelanzahlkonzentration yon Aerosolen, Dissertation, Univ. Duisburg, Germany. /4/Dr0tboom, M. (1994), Entwicklung einer Anordnung zur Beschleunigung elektr, gel. Partikel in FluBrichtung eines schutzluftumhiillten Aerosolstrahles, Diplomarbeit, Univ. Duisburg, Germany.
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