BT CGA-411 Operation Manual page 21

electrically insulated handle. Bar hole probes are designed to be attached to the water block
filter on the coiled hose. A more convenient hose for bar hole measurements, five feet of
straight tubing, is available as Part No. SH-060.
CAUTION: Hold the steel bar hole probe only by the insulated handle to avoid electrical
shock from buried power lines.
Dust and Water-block Filter
A Teflon® filter removes particles of dust and dirt and blocks water. The white disk in
the filter should be inspected periodically for accumulated dirt which may slow air sampling. A
filter can be cleaned by removing the probe and tapping the filter on a hard surface to remove dry
dust and dirt. Do not insert objects into the water block filter while attempting to clean it as they
may puncture the Teflon. Typically, the filter needs to be replaced once or twice a year.
Replacement water-block filters are available as Part No. WF-305 (package of 5 filters).
Inlet Dust Filter
Removal of the intake connector (used to attach the sampling hose) exposes a metal filter
cup pressfit onto the intake. These filters are not a substitute for water-block filters since they
will not block water. If this filter gets blocked, it may be cleaned with compressed air or
replaced.
Water-block Filter for Gooseneck Probe
A Teflon® filter, housed in a knurled nut, removes particles of dust and dirt and blocks
water (see the Dust & Water-block Filter section above for details on cleaning). Replacement
filters are available as Part No. WF-205 (package of 5 filters).
WARNING: Do not use a Gas-Sentry without a dust and water-block filter. Do not use
a dust and water-block filter with a puncture in the Teflon disk.
Fig. 3. Dust and water-block filter.
Fig. 4. Water-block filter for gooseneck probe.
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