7
CONSIDERATIONS
5
Ambient Light
- The optical collection system collects the light pulses from the
particulate matter suspended in the liquid. Light from other sources can possibly
interfere if a sufficient quantity enters the collection system. Normal levels of
incandescent illumination will not usually provide significant interference but high
levels of illumination may cause trouble and should be checked. Fluorescent
light, because of its high flicker content, are especially troublesome in this regard
and should be avoided. A light-tight cover is provided to eliminate fluorescent
light effects and is strongly recommended.
Beam Absorption
- The projected laser beam can be absorbed or scattered by
the container wall or the liquid under analysis. For most clean container walls and
most relatively clear liquids, this absorption is negligibly small and will not affect
the instrument calibration. If the liquid is optically absorbing or contains very fine
particles (typically < 1 µm in diameter) the amount of light scattered into the
photodetector will be reduced. When measurements are made with such a liquid,
the opacity meter is used to give precise opacity and dilution down to 10%
opacity is recommended in order to detect particles down to 1µm in diameter.
Optical and Electrical Background
- When viewing particles with an optical
microscope, it is necessary to clearly distinguish particles from the background in
order to get an accurate count. With the Spectrex PC-2300, it is similarly
necessary that the instrument be able to clearly distinguish particles from the
background in order that they are counted accurately. The background in this
case consists of both optical and electronic noise and is referred to as the
“background level”.
Summary of Contents for PC-2300
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