A depth gauge is a pressure gauge that displays the equivalent depth in water. It is a piece of diving equipment

Diving equipment

Diving equipment is equipment used by underwater divers for the purpose of facilitating diving activities. This may be equipment primarily intended for this purpose, or equipment intended for other puprposes which is found to be suitable for diving use....

 often used by SCUBA divers

Scuba diving

Scuba diving is a form of underwater diving in which a diver uses a scuba set to breathe underwater....

.

Most modern diving depth gauges have an electronic

Electronics

Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...

 mechanism and digital

Digital

A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...

 display. Older types used a mechanical

Machine

A machine manages power to accomplish a task, examples include, a mechanical system, a computing system, an electronic system, and a molecular machine. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work...

 mechanism and analogue display.

A diver uses a depth gauge with decompression tables and a watch

Watch

A watch is a small timepiece, typically worn either on the wrist or attached on a chain and carried in a pocket, with wristwatches being the most common type of watch used today. They evolved in the 17th century from spring powered clocks, which appeared in the 15th century. The first watches were...

 to avoid decompression sickness

Decompression sickness

Decompression sickness describes a condition arising from dissolved gases coming out of solution into bubbles inside the body on depressurization...

. A common alternative to the depth gauge, watch and decompression tables is a dive computer

Dive computer

A dive computer or decompression meter is a device used by a scuba diver to measure the time and depth of a dive so that a safe ascent profile can be calculated and displayed so that the diver can avoid decompression sickness.- Purpose :...

. A depth gauge and an oxygen analyser/oxygen sensor

Oxygen sensor

An oxygen sensor, or lambda sensor, is an electronic device that measures the proportion of oxygen in the gas or liquid being analyzed. It was developed by the Robert Bosch GmbH company during the late 1960s under the supervision of Dr. Günter Bauman...

 can be used to measure the partial pressure

Partial pressure

In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture....

 of oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 of the breathing gas

Breathing gas

Breathing gas is a mixture of gaseous chemical elements and compounds used for respiration.Air is the most common and only natural breathing gas...

, which is necessary to avoid oxygen toxicity

Oxygen toxicity

Oxygen toxicity is a condition resulting from the harmful effects of breathing molecular oxygen at elevated partial pressures. It is also known as oxygen toxicity syndrome, oxygen intoxication, and oxygen poisoning...

.

Digital depth gauges commonly also include a timer showing the interval of time that the diver has been submerged. Some show the diver's rate of ascent and descent, which can be is useful for avoiding barotrauma

Barotrauma

Barotrauma is physical damage to body tissues caused by a difference in pressure between an air space inside or beside the body and the surrounding fluid...

.

As the gauge only measures water pressure, there is an inherent inaccuracy in the depth displayed by gauges that are used in both fresh water

Fresh Water

Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...

 and seawater

Seawater

Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...

 due to the difference in the densities

Density

The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...

 of fresh water and seawater.

External links

Articles on depth gauges hosted by the Rubicon Foundation

Rubicon Foundation

Rubicon Foundation, Inc. is a non-profit organization devoted to contributing to the interdependent dynamic between research, exploration, science and education. The foundation, started in 2002, is located in Durham, North Carolina and is primarily supported by donations and grants. Funding has...