Gauges
A diver relies on scuba gauges to
know three things:
- Depth
- Air Consumption
- Time
Depth and Time are vital for nitrogen
and air management. A scuba diver
needs to know how deep he has been
and for how long in order to judge
the necessity and length of decompression
stops and to calculate residual
nitrogen for repetitive dives.
The time of
a dive is easily tracked using
a diving watch and the depth
is tracked
using a depth gauge.
Scuba gauges are almost always sold
as an integrated console. With a
single console, the scuba diver has
one piece of equipment, attached
by a hose to the tank, which shows
current depth and tank pressure.
The console may be either encased
in a rubber sheath called the "gauge
boot" or embedded in a hard
plastic shell. Sometimes the consoles
are simply two dials - tank pressure
and depth - embedded in a handheld
device. Other consoles will integrate
more than two dials: they might include
a compass, timer, temperature gauge
or other instrumentation. Consoles
can often be disassembled and reconfigured
so that the depth gauge can be replaced
by a dive computer.
Even when nitrogen management is
left to a dive computer air consumption
is shown on a separate dial. If the
diver is using a wrist-mounted computer
the console may only have a tank
pressure gauge.
In addition to the depth and time,
the scuba diver needs to know how
much air is in the scuba tank. At
the beginning of the dive the diver
starts between 200bar and 232bar.
The diver watches the air pressure
gauge for several reasons:
- To know how much air is left
- To know how much time can be
spent
- To determine a good time to start
ascending
- To see if any of the equipment
(BCD, regulator, hoses) are
leaking
- To see if the valves are
working properly
If the valves are working properly
and delivering proper air pressure
the diver should be able to breathe
from the regulator and the gauge
will not move (except slowly, downward).
If the pressure gauge dips with
every breath then there is not
enough pressure
coming from the tank and there
may be a problem with the scuba
tank,
valve, or hose. Another reason to have a scuba tank
pressure gauge: It is important to
stop diving with air still remaining
in your tank. A good recommendation
is to get back on the boat with at
least 50bar still in the tank. Not
only does this make sense from a
conservative safety point of view,
but another important reason a diver
should never decompress a scuba tank
is that the air pressure prevents
contaminants, water in particular,
from getting into the tank. Water
is not clean. When water gets into
a scuba tank (if it is a steel tank)
it causes rust, mildew, mould and
bacteria to flourish inside. The
scuba tank must then be sterilized,
dried and refilled.
When shopping for scuba gauges for
your scuba system, look for:
- Ergonomic grip
- Long-term warranty
- Luminescent indicators or backlighting
options
- Rotating / swivel mounting
- Easy disassembly for cleaning
or replacing parts
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