4 | Overview
HYDAC FILTER SYSTEMS GMBH
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BeWa FCU1210 3545830b en-us lq
4.1 Counting contaminant particles optically (light
blockade procedure)
The measuring principle of the light blockade procedure is
shown in simplified form in the following sketch.
The light source transmits monochromatic light through the
flow of oil to a photo detector, which produces a particular
electrical signal. If a particle gets between the light source and
the photo detector, then a shadow will be cast on the photo de-
tector.
This shadow causes a change in the electrical signal gener-
ated by the photo detector. This change makes it possible to
determine the size of the shadow cast by the particle and thus
to gauge the size of the particle itself.
This procedure makes it possible to determine the cleanliness
class according to ISO 4406, NAS 1638 and SAE AS 4059.
The disruption factors of this measurement principle are, for
example, foreign fluids and small gas bubbles that lead to re-
fractions, thus causing them to be counted as particles as well.
Fig. 4:
Light blockade procedure
1 Light source
2 Contaminant particle
3 Photo detector
Содержание FCU 1210
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