FCU 1000 Series
Counting particles in the FCU 1000
HYDAC FILTER SYSTEMS GMBH
en
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BeWa_FCU1000_3371346d en-us 2010-11-24.doc 2010-11-24
Counting particles in the FCU 1000
The measuring principle of the light blocade 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
detector.
This shadow causes a change in the electrical signal generated 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 4406:1987, ISO 4406:1999, NAS 1638 and SAE AS 4059.
The disruption factors of this measurement principle are foreign fluids and small gas
bubbles that lead to refractions, thus causing them to be counted as particles as
well.
Each of the signal peaks corresponds to the shadow cast by one particle. The signal
height or amplitude reflects the particle size. Thresholds are used to classify the
particle sizes >2, >5, >15, >25 µm or >4, >6, >14, >21 µm
(c)
.
Threshold values
Time
Flow of oil
Flow of oil
Particles
Photo detector
Light source
Light source
Photo detector
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