Editing Depth gauge (section)

=== Pneumofathometer ===
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[[File:Gas panel 1.png|thumb|left|Surface supplied diving gas panel for one diver:
{{unbulleted list|PG: pneumofathometer gauge |OPV: overpressure valve |PS: pneumo snubber |PSV: pneumo supply valve |DSV: diver supply valve |MP: manifold pressure |RSV: reserve supply valve |RP: reserve pressure |MSV: main supply valve |SP: supply pressure |RGS: reserve gas supply |MGS: main gas supply |UP: umbilical pneumo hose |UB: umbilical breathing gas hose |DP: depth measured by pneumofathometer }}]][[File:Pressure gauge on Siebe Gorman manual diver's pump P3220126.jpg|thumb|Pressure gauge on Siebe Gorman manual diver's pump, indicating delivered pressure in pounds per square inch (black) and feet sea water (red)]]
[[File:Surface supply air panel for 4 divers P3053737.jpg|thumb|Surface supply air panel with supply pressure gauges (small) and pneumofathometer gauges (large diameter). Three of the four "pneumo lines" are blue.]]
A pneumofathometer is a depth gauge which indicates the depth of a surface supplied diver by measuring the pressure of air supplied to the diver. Originally there were pressure gaues mounted on the hand cranked [[diver's air pump]] used to provide [[breathing air]] to a diver wearing [[standard diving dress]], with a free-flow air supply, in which there was not much back-pressure other than the hydrostatic pressure of depth. As [[non-return valve]]s were added to the system for safety, they increased back pressure, which also increased when demand helmets were introduced, so an additional small diameter hose was added to the diver's umbilical which has no added restrictions and when a low flow rate of gas is passed through it to produce bubbles at the diver, it gives an accurate, reliable and rugged system for measuring diver depth, which is still used as the standard depth monitoring equipment for surface supplied divers. The pneumofathometer gauges are mounted on the diver's breathing gas supply panel, and are activated by a valve. The "pneumo line", as it is generally called by divers, can be used as an emergency breathing air supply, by tucking the open end into the bottom of the helmet or full face mask and opening up the valve to provide free flow air. A "gauge snubber" needle valve or orifice is fitted between the pneumo line and the gauge to reduce shock loads on the delicate mechanism, and an overpressure valve protects the gauge from pressures beyond its operating range. The type of high precision gauge used is also known as a [[caisson gauge]]. Precision is typically 1% to 0.25% of full scale.