Depth gauge

Classic depth gauge for divers, 0–80 m

Depth gauge in a Type 205 submarine

The depth gauge is a pressure measuring device (manometer) to determine the current depth under water in relation to the surface of the water ( diving depth ). The depth gauge is an important part of the diving equipment and shows the diver his current and mostly his maximum diving depth. In submarines , he is also used in diving trip to determine the depth of the boat.

In contrast, for measuring the water depth in the sense of the distance measurement for a body of water in the shipping a solder , a sonar or some other form of echolocation used, while in the bathymetry and optical methods such. B. Laser scanning can be used.

functionality

Because the ambient pressure increases with increasing water depth (1 bar to 10 m), the pressure difference to the water surface and thus the exact diving depth can be determined by measuring it.

Designs

Boyle-Mariottescher depth gauge

The Boyle-Mariottesche depth gauge consists of a circularly curved glass tube open on one side. It has no moving parts. When diving, the water penetrates the tube and, depending on the depth, compresses the air in it. The edge of the air bubble in the tube shows the depth on a scale . In the depth range up to 10 m this depth gauge shows quite precisely. Because the pressure in this range doubles from 1 to 2 bar, half of the scale is available for this. At greater depths, the display becomes more and more imprecise. The maximum diving depth cannot be recorded with this depth gauge.

Bourdon tube

Pipe depth gauge

The tube spring depth gauge consists of a bent tube made of resilient metal, the Bourdon tube , to which the water pressure is applied depending on the design of the depth gauge from the inside or from the outside. As the pressure increases, the tube stretches; when it decreases, it returns to its original curvature. This movement is transmitted to a pointer , which can mark the maximum diving depth reached with a drag pointer. The accuracy of the display is good.

Membrane depth gauge

With the membrane depth gauge, the water pressure acts on a flexible metal can, which is compressed more and more as the water pressure increases. The movement of the membrane is also transferred to a pointer and, if necessary, a drag pointer. The accuracy of the display is very good.

Modern dive computer with integrated depth gauge

Dive computer

A depth gauge is integrated in dive computers , the measured values of which are digitized and used to calculate the current no-stop or decompression time. The diving depth is shown as a number on the display along with the other values and recorded by the computer for continuous simulation of the decompression model . Most dive computers contain a piezoelectric pressure sensor . Capacitive or inductive pressure sensors are also rarely used.