Feature: Scuba Diving Watch

This month we take a close look at the ultimate in dive computers and navigation - combined.

The SUUNTO D9 :

The new Suunto D9 is the world’s first dive computer to integrate a digital compass and wireless tank data reception.

Underwater a diver must monitor several gauges to get the crucial information for a dive: depth, time, tank pressure, decompression status, direction, just to name a few. The Suunto D9 combines all dive critical information in one instrument, conveniently on your wrist. Instead of monitoring a multitude of gauges, the diver can concentrate on what is important, diving.

The Suunto D9 is the world’s first scuba diving watch and dive computer to incorporate a digital compass. The compass shows the general direction with a graphical compass rose, as well as the exact bearing with the numerical display. Headings can be stored in Suunto D9’s memory for later analysis. And the compass can naturally be used on land, too.

By using the Suunto D9’s optional wireless transmitter, the diver can also monitor tank pressure and air consumption data from the wrist. The remaining tank pressure is displayed both numerically and graphically, and an estimation of the remaining air time is given throughout the dive. This allows the diver to monitor the remaining air supply at the same time he monitors depth and time. Real time air-consumption is also stored in the memory.

The Suunto D9 can be used with up to three different gas mixes containing 21-100% O2, allowing gas switching during the dive. Decompression calculations are based on the Suunto RGBM model, which provides iterative deep stops (see below)  as an alternative to traditional safety stops. For those intending to go really deep the maximum depth display is set to 200m [660ft].

The built in dive-logbook provides, in addition to basic dive data, a graphical dive profile where real time water temperature and tank pressure data can be analysed on the wristop computer. The sampling rate can be set to as low as 1s.

This beautifully designed Suunto D9 scuba diving watch has a titanium housing and includes an USB-compatible PC interface and the Suunto Dive Manager 2.0 software.

DEEP STOPS:

Deep stops allow you to complete your safety stops at depth. The amount of stops needed, as well as the depth at which they are required, depends on the maximum depth reached during the dive.

The dive computer calculates half the pressure difference between the maximum depth and the ceiling depth. This determines the first deep stop depth. Deep Stop calculations determine the next stop by using the last Deep Stop depth as the maximum depth, and the current ceiling until you are within 18 meters/60 feet of the ceiling. At this point, continuous decompression is employed.

More about the Suunto Decompression Algorithms:

Classical Haldane-type decompression calculation assumes that all gas is dissolved into the tissues, and remains dissolved as long as the maximum tissue tensions are not exceeded.

Bubbles are assumed to form only when the ascent rate or the m-values are exceeded. As the pressure gradient is inversley proportional to the surrounding pressure, the diver is brought as shallow as possible, as fast as possible, in order to maximise offgassing.

Doppler-studies however show, that microbubbles are present on all dives. Therefore the effects of free gas need also to be considered in decompression calculations.

The Standard Suunto RGBM Algoritm:

The Suunto RGBM was designed to protect the recreational diver from the effects of micro-bubble build-up. It encorpororates a bubble-factor based tracking system to adapt the decompression requirement based on conducted dive profiles.

The maximum ascent rate is set to 10m/min.

Continuous decompression provides maximum offgassing and a clean decompression curve.
A 3min recommended safety stop is added to all dives deeper than 10m.
Mandatory Safety stops are added to deal with adverse ascent rate violation.
An extended surface interval is prompted when microbubbling is present.

The Suunto Deep Stop RGBM Algorithm:

The Suunto Deep Stop RGBM algorithm increases microbubble suppression on deep dives even further by introducing iterative deep stops. The first deep stop is placed at half the pressure difference between your maximum depth and the ceiling depth. Once the deep stop depth is attained, the next deep stop will again be introduced half-way to the ceiling, and so on. Once the ceiling depth is reached, continous  decompression is employed for staging the end of the profile.

In the Suunto D9 the user can choose between the familiar Safety Stop providing Suunto RGBM, or the new Deep Stop RGBM.