OPERATING MANUAL CD 2000
Palas
®
GmbH, Karlsruhe, Version V002022014
5. Electrical Adjustment of Corona Ionization Chambers
In order to assure a correct function of the discharge unit, it is important that the electrical
working point is adjusted in the right way.
5.1 Principle:
The current from the negative and positive high-voltage supplies is set to a value so
high that it is completely carried by the corona-discharge. No, or only a few sparks
are allowed. This current is set by adjusting the current limiting circuit of the high voltage
supplies to the chosen value of maximum current.
The voltage limit is set a little higher than necessary for the maximum current. Due
to this, the current will always keep its value, even if conditions such as temperature or
state of electrodes are changing.
5.2 Procedure:
Positive and negative high-voltage supply and discharge unit are independent of
each other and can be separately adjusted.
1) Start operating the discharge unit but without aerosol supply. (See First Set-up)
Recommendation: Mixing air volume flow should be set to 5 m3/h (4 to 10 m3/h is
useable).
Connect digital voltmeter to the monitor-output on the back side of the high-
voltage supply unit:
as first to the monitor output for Imon of the positive high voltage part; after this
part is set, then connect the voltmeters to the 'negative' part.
Setting for voltmeter is: voltage measurement 0 to 10 V.
2) The adjusting potentiometers are mounted on the front plate. They have a scale
from 0 to 999 and can be set easily and reproducible by hand.
5.3 Adjusting the external potentiometers with scale:
Relation between scales and voltage or current:
voltage (Upos/Uneg): 1000 scales correspond to 6000 V
1 scale corresponds to 6 V
current (Ipos/Ineg): 1000 scales correspond to 1000 µA
1 scale correspond 1 µA
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