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circuitry and power sources must be protected from the corrosive properties of
seawater and biofouling by aquatic organisms. Moreover, submersible vehicles or
submerged emplacements may not provide protection from the environment.
Indeed, in many vehicles the payload bays are open to the seawater medium under
local hydrostatic pressure. Most submersible instruments are designed as self-contained units encased in their own pressure hull.
Modern instruments designed for submerged autonomous deployment are commonly contained in cylindrical pressure housings or, in some special cases, in spherical housings. Depending on the depth of the application, different pressure hull
materials may be used ranging from PVC and acrylic for shallow water applications, to anodized aluminum or DELRIN (a polyoxymethylene polymer formulation of exceptional density, stability hardness, and rigidity) for intermediate depths
and stainless steel, titanium, or spherical glass for very deep water.
One or both endcaps on cylindrical housings may be removable for access to
electronics and batteries. Such endcaps may be disc-shaped to cover the end of the
housing with an O-ring seal flush to the cylinder wall edge. Endcap to cylinder wall
junctions may be secured by bolts through the endcap penetrating the threaded cylinder wall or endcap and cylinder may be affixed with nuts and bolts if the cylinder
ends are flanged, as is often the case for steel or aluminum housings. More commonly a shoulder endcap is machined so that a flange covers the cylinder end and
the endcap body penetrates a few centimeters into the cylinder and seals with one or
more additional O-rings between endcap and cylinder. Nylon bolts may replace
steel bolts to circumvent corrosion but due consideration must be given to their relative fragility.
Specialty steel or titanium cages may be provided for high exposure applications
where the fragile instruments may be in danger of severe shock such as vertically
deployed instruments or instruments mounted in-line on a mooring cable for which
deployment and recovery maneuvers are particularly hazardous. To affix cylindrical
pressure housing instruments to the platform deck or the cage structure as may be
the case, half-moon indents are machined into PVC or DELRIN base block pairs to
fit the cylinder diameter. The instrument is seized to the blocks using various steel
or plastic hose-clamp systems or with bolted-on complementary half-moon bracket
clamps of the same block material. The base blocks are threaded or perforated for
mounting aboard the platform with hex-head bolts or U-bolts. Bottle mounts, common to CTD/carousel packages, may be adapted for instrument deployment aboard
the carousel in place of oceanographic sampling bottles.
External sensors such as a thermistors or conductivity bridges require connection
across the pressure hull to the power source and system electronics. In addition,
data communication ports are usually required. These connections are commonly
achieved using waterproof bulkhead-mounted wet-pluggable connectors readily
available from specialized manufacturers in a variety of configurations.
Optical sensors may be housed within the pressure housing and need only optical
windows which can be integrated into the pressure housing such as is found in fluorometers or optodes. Specialized optical instruments operating in the UV must
employ materials transparent to UV such as crystalline quartz for optical windows.
4.2 Ocean Observing Instrument Mounts and Housings
circuitry and power sources must be protected from the corrosive properties of
seawater and biofouling by aquatic organisms. Moreover, submersible vehicles or
submerged emplacements may not provide protection from the environment.
Indeed, in many vehicles the payload bays are open to the seawater medium under
local hydrostatic pressure. Most submersible instruments are designed as self-contained units encased in their own pressure hull.
Modern instruments designed for submerged autonomous deployment are commonly contained in cylindrical pressure housings or, in some special cases, in spherical housings. Depending on the depth of the application, different pressure hull
materials may be used ranging from PVC and acrylic for shallow water applications, to anodized aluminum or DELRIN (a polyoxymethylene polymer formulation of exceptional density, stability hardness, and rigidity) for intermediate depths
and stainless steel, titanium, or spherical glass for very deep water.
One or both endcaps on cylindrical housings may be removable for access to
electronics and batteries. Such endcaps may be disc-shaped to cover the end of the
housing with an O-ring seal flush to the cylinder wall edge. Endcap to cylinder wall
junctions may be secured by bolts through the endcap penetrating the threaded cylinder wall or endcap and cylinder may be affixed with nuts and bolts if the cylinder
ends are flanged, as is often the case for steel or aluminum housings. More commonly a shoulder endcap is machined so that a flange covers the cylinder end and
the endcap body penetrates a few centimeters into the cylinder and seals with one or
more additional O-rings between endcap and cylinder. Nylon bolts may replace
steel bolts to circumvent corrosion but due consideration must be given to their relative fragility.
Specialty steel or titanium cages may be provided for high exposure applications
where the fragile instruments may be in danger of severe shock such as vertically
deployed instruments or instruments mounted in-line on a mooring cable for which
deployment and recovery maneuvers are particularly hazardous. To affix cylindrical
pressure housing instruments to the platform deck or the cage structure as may be
the case, half-moon indents are machined into PVC or DELRIN base block pairs to
fit the cylinder diameter. The instrument is seized to the blocks using various steel
or plastic hose-clamp systems or with bolted-on complementary half-moon bracket
clamps of the same block material. The base blocks are threaded or perforated for
mounting aboard the platform with hex-head bolts or U-bolts. Bottle mounts, common to CTD/carousel packages, may be adapted for instrument deployment aboard
the carousel in place of oceanographic sampling bottles.
External sensors such as a thermistors or conductivity bridges require connection
across the pressure hull to the power source and system electronics. In addition,
data communication ports are usually required. These connections are commonly
achieved using waterproof bulkhead-mounted wet-pluggable connectors readily
available from specialized manufacturers in a variety of configurations.
Optical sensors may be housed within the pressure housing and need only optical
windows which can be integrated into the pressure housing such as is found in fluorometers or optodes. Specialized optical instruments operating in the UV must
employ materials transparent to UV such as crystalline quartz for optical windows.
4.2 Ocean Observing Instrument Mounts and Housings