Amron 8225-HP, Instruction Manual

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THEORY OF OPERATION
MECHANICAL (cont’d) 9.1
The pneumo system operates on the bases of a tube extending from the surface of the water to
the depth at which the measurement is going to be taken. Air (pressurized) is forced into the tube,
until all the water is forced out of the tube. In fact, bubbles of air will come out of the end hose.
The air is then shut OFF, (this eliminates any additional pressure from flow) the pressure will then
stabilize equal to the pressure at the end of the hose. The pressure in the hose will then equal the
pressure at the end of the hose, and the depth.
The pressure is then read on a very accurate gauge. The dial of the gauge is calibrated in Feet of
Seawater rather than Pounds per Square Inch (PSI), eliminating the need to convert from PSI to
FSW.
The pneumo gauges have a 6-inch dial, dual scale 0-250 FSW/0-76 MSW, with 1-foot calibration
increments. The accuracy of the gauge is 0.25% of full scale. Gauges are supplied with calibration
certificates traceable to the National Bureau of Standards. The gauges must be Calibrated every
six months to guaranty their accuracy. Gauges should be cross checked before every dive, if there
is a discrepancy of more than 2% between gauges, the gauges must be calibrated before being
placed in service.
Pneumo valves, one for each diver, shut off type valve, KEL-F seat for positive shut-off.
Pneumo gauge protectors, each pneumo gauge is protected by an automatic valve which is
factory set to shut off all pressure to the gauge when the pressure reaches or exceed the set
point. The set point for a slow rising pressure is approximately 10% above full scale, 122 PSI. Fast
rising pressures will be shut off at a lower pressure. The gauge protector will automatically release
when the pressure is reduced. The gauge protector also includes a gauge snubber to protect the
gauge from pulsations (shocks) in the pressure applied to the gauge.
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