How Diving Gauges Work

Diving gauges are ubiquitous pieces of equipment.

They sit at the end of your high-pressure hose, right above your air gauge, faithfully ticking off the depth as you rise and fall in the water column. They’re vital to dive planning and planning your air consumption, yet few people give much thought to these lonely little gauges.

How do they work?

Are they simple or do they require a degree in engineering to understand?

We know diving gauges are good little soldiers

They perform their duty day in and day out without fail. Seriously; these things hardly ever fail.

If your equipment made up a senior high school class, your diving gauges would be voted “least likely to have any problems ever.” This fact seems to suggest that diving gauges have a simple construction.

It’s one of the laws of life that the more complicated something is, the more likely it is to break. The fact that depth gauges are the proverbial “lead sled” suggests that they’re so simple a child could understand them.

As it turns out, the most common pressure gauges use an extremely simple device called a bourdon tube. This is a metal tube the curves around the inside of the pressure gauge with one side accepting the pressure and the other side attached to a device that moves the needle.

As you go deeper in the water column, the pressure increases. As the pressure increases it depresses the pressure-sensitive end of the bourdon tube which, in turn, causes the pressure inside the tube to increase and the tube to flex outward.

As the tube flexes outward, it pulls the device attached to the needle which then moves the needle to indicate the depth. It’s a simple process and it’s accurate enough to be used for diving purposes.

Alternative Depth Gauges

Of course, there are other kinds of depth gauge mechanisms such as digital depth gauges that use transducers to measure pressure and capillary depth gauges that use the water to compress air in a tube.

Both of these depth gauges have their advantages and disadvantages. For example, a digital depth gauge will be more accurate than a diving gauge that uses a bourdon tube, but they’re more likely to fail because of their electronic components.

Capillary depth gauges, on the other hand, are cheaper than depth gauges that use a bourdon tube, but they’re far less accurate.

In fact, many people consider capillary depth gauges to be worthless at depths greater than 40 feet.

For simplicity and dependability, nothing beats the bourdon tube depth gauges. Fortunately, these gauges are also the most commonly available. While it’s true that digital depth gauges are more accurate, the difference is minor─ nowhere near enough to have any impact on your dive planning.

It’s nice to find a technical device that’s so reliable in a world of rapidly developing technologies, extended warranties, and shall we say, less than durable materials.

There’s no more durable piece of equipment than your lowly, faithful depth gauge.

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