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OBS-3A Turbidity and Temperature Monitoring System
9.5 Pressure Housing
The pressure housing and O-ring seals
require little maintenance unless the
housing has been opened since the last service. However, it should be
carefully inspected every six months and serviced before all deployments
longer than one month.
1.
Disassemble O-ring seals and inspect mating surfaces for pits and
scratches.
2.
Inspect O-rings for cuts and nicks; replace if necessary using spares
provided.
3.
Clean O-rings and mating surfaces with a cotton swab and alcohol.
Remove fibers from groove and mating surfaces then grease O-rings with
DOW Compound 55 and reassemble.
9.6 Antifoulant Coatings
Clear TBTA antifoulant coating or toxin-impregnated collars can be used for
monitoring in biologically active waters. TBTA prevents most marine algae
and encrusting animals from growing on optical surfaces for up to two months
with minimal loss of IR transmission. It is illegal to use TBTA in many places
so check applicable water quality regulations in your area before using TBTA
coated OBS sensors. Use of TBTA is the sole responsibility of the user
.
9.7 User-serviceable Parts
Alkaline D cells and the components of the 21229 Accessory Kit can be
purchased as replacement parts. Campbell Scientific model numbers and
product descriptions follow:
CSI pn 20990 End Cap O-ring
CSI pn 21145 Pressure Sensor Spring Clip
CSI pn 21135 End Cap Screws, 8-32 x 3/8 in, socket (5/64 in)
CSI pn 21120 Dummy Plug
CSI pn 21122 Plug Locking Sleeve, Subconn® MCDLSF
CSI pn 425 Alkaline D-Cells Batteries
CSI pn 21136 Screws, #4-40 x 1/4 in, socket
CSI pn 20792 OBS-3A Test Cable, 2 m (6.5 ft)
CSI pn 21149 Hex Driver, 5/64 in
10. Factors Affecting OBS Response
This section summarizes some of the important factors that affect OBS-3A
measurements and shows how ignoring them can lead to erroneous data. If you
are certain that the characteristics of suspended matter will not change during
your survey and that your OBS was factory calibrated with sediment from your
survey site, you only need to skim this section to confirm that no problems
have been over looked.
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