Wet Labs ac-s, Руководство пользователя

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22 ac-s User’s Guide (ac-s) Revision F 9 Feb. 2006
6. Technical Reference
Figure 10 shows a diagram of the ac-s. The unit consists of two pressure housings separated
by an aluminum “unistrut” frame. The “bottom” pressure cylinder houses the light sources,
filter wheel, motor controller and transmitter optics. The “top” can houses the receiver optics
and the control and acquisition electronics for the unit. The absorption and attenuation beam
paths and flow tube assemblies are between the receiver and transmitter housings. Power and
communications in and out of the unit are provided via the 6-pin bulkhead connector at the
end of the receiver housing.
6.1 Mechanical
The ac-s is housed in two robust pressure housings made from acetal copolymer,
separated by an anodized aluminum unistrut frame.
The flow tube assemblies are integral to the optical behavior of the ac-s. They are optical
components that help produce a very precise measurement, and thus they need to be dealt
with accordingly. Before using, inspect both tubes and make sure they are free of stains
and dust. The reflective flow tube for the absorption measurement operates using the
principle of internal reflection. To maintain its reflective properties, it requires a thin air
gap between the outer wall of the quartz tube and the inner wall of the surrounding
sleeve. The reflective tube should be periodically checked for leaks. To determine if the
tube is maintaining its reflective properties, immerse it in water and point towards a fairly
light background. The inside of the tube should appear uniformly bright. If the tube has
leaked, call the factory for repair instructions or tube replacement.
6.2 Optics
The ac-s performs concurrent measurements of the water’s attenuation and absorption
characteristics by incorporating a dual path optical configuration in a single instrument.
Each path contains its own source, optics, and detectors appropriate to the given
measurement. The two paths share a common filter wheel, control and acquisition
electronics. For purposes of description, we refer to the beam performing the attenuation
measurement as the
c beam
(Figure 7) and the beam used to make the absorption
measurement as the
a beam
(Figure 8).