Submersible Pressure Gauge

There are two types of submersible pressure gauges (SPG):



Both types of SPGs will show the remaining pressure in the scuba diver’s tank. With the proper calculations, a scuba diver will be able estimate the remaining time allowed (based on air consumption) that they have underwater.

Mechanical SPGs use what is called a Bourdon tube design. The Bourdon tube is shaped like the letter C. As pressure is exerted through a diaphragm into an oil filled chamber with the Bourdon tube installed, the Bourdon tube will flex according to the pressure. As the Bourdon tube flexes, it will in turn move a mechanically linked needle around the dial to reflect the pressure being exerted. If you ever notice that the oil has leaked out or is leaking, it is time to replace or repair your SPG.

Digital SPGs use a different mechanism to detect pressure. As the pressure exerts itself onto the SPG’s diaphragm, the increase pressure affects the voltage across a specially designed coil. This diaphragm and coil assemble is commonly called a pressure transducer. The change in voltage can be read as a change in pressure. As with any sensitive electronic component, strong magnetic fields can disrupt the reading across the coil.

Both mechanical and digital SPGs can be ordered with metric or imperial read outs, to aid in their use. This is a good time to remind divers that as they travel the world, they should be familiar with the minimum air pressure in the measurement unit of their rental SPG. The two ways to measure air pressure are Pounds per Square Inch (PSI) or BAR (a unit of pressure equivalent to a million dynes per square centimeter – you wanted to know!). I recommend that a diver returns with at least 500 PSI or 34.5 BAR in their tank.

Since all divers need to know their air pressure underwater, the submersible pressure gauge is the main gauge in all diving consoles.

Because of the sensitive nature of the submersible pressure gauge, many divers want to hand carry their instruments with them. A quick disconnect is a valuable way of disconnecting the high pressure hose from the diving console.

If a diver does not want a full diving console on their scuba tank because it is a redundant or bail-out bottle, check out our pin gauges on our

Bail-out bottle page.

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