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Suunto DX User Guide

Dive modes

Suunto DX has the following dive modes:

  • Air: for diving with regular air
  • Mixed: for diving using oxygen-enriched and helium gas mixtures
  • CCR: for rebreather diving
  • Gauge: for using the dive computer as a bottom timer
  • Off: turns dive mode off completely; the dive computer does not automatically switch the dive mode when submerged and dive planning mode is hidden

By default, Air mode is activated when you enter dive mode. You can change which mode is activated or turn dive mode off under the general settings.

To change dive modes:

  1. While in time mode, keep DOWN pressed.
  2. Press SELECT to enter Dive Mode.
  3. Change to the desired mode with UP or DOWN and confirm with SELECT.
  4. Press MODE to exit.

Each dive mode has its own settings which you need to adjust while in the given mode.

To modify dive mode settings:

  1. While in a given dive mode, keep DOWN pressed.
  2. Press DOWN or UP to scroll through the settings.
  3. Press SELECT to enter a setting.
  4. Adjust the setting with DOWN or Up and confirm with SELECT.
  5. Press MODE to exit.
NOTE:

Some settings cannot be changed until five (5) minutes have elapsed after the dive.

Air mode

Air mode is for diving with regular air and has the following settings:

Mixed mode

Suunto DX has a mixed dive mode for diving with oxygen and/or helium mixture in an open system.

Mixed mode has the following settings available:

In mixed mode, the default setting is standard air (21% O2 and 0% He), and oxygen partial pressure (PO2) is 1.4 bar (20 psi).

The default setting for maximum oxygen partial pressure is 1.4 bar (20 psi). Valid values are 0.5-1.6 bar (7-23 psi).

Changing gases on multi-gas dives

If you have using more than one gas on a dive, Suunto DX allows you to change enabled gas mixes during the dive.

A dive is always started with Mix1. You can change to another enabled mix that is within the set maximum oxygen partial pressure. The tissue calculation during the dive is based on the mixes you have selected as Primary gases.

To change gases during a dive:

  1. Keep UP pressed.
  2. Scroll through the enabled mixes with UP or DOWN and select the gas you want to use with by pressing SELECT.
NOTE:

If no button is pressed within 15 seconds, the dive computer goes back to the dive display without changing the gas mix.

The mix number, O2% and PO2 for the mixes are shown when scrolling. If the set PO2 limit is exceeded, the PO2 value blinks. You cannot change to the gas in this case. The mix is shown, but you cannot select it to use.

When ascending, Suunto DX prompts you to change gas when the PO2 level you have set for the next mix allows a gas change.

CCR mode

CCR mode is a dive mode dedicated to rebreather diving.

The CCR mode has the following settings:

In CCR mode you can define up to three diluent gases and up to eight bailout gas mixes. Use the setpoint settings to define your high and low set points and switch depths (see Setpoints).

Closed-circuit gases

On a rebreather dive, you need at minimum two closed-circuit gases: one is your pure oxygen tank, and the other is a diluent.

The correct oxygen and helium percentages of the diluent gas(es) in your diluent cylinder(s) must always be entered into the dive computer (or through DM5) to ensure correct tissue and oxygen calculation. Diluent gas(es) used on a rebreather dive are found under CC gases in the main menu.

To modify diluent gases

  1. While in CCR mode, keep DOWN pressed to enter settings.
  2. Press SELECT to enter CC Gases settings.
  3. Diluent 1 is displayed and is always on (cannot be turned off).
  4. Press SELECT to move to the oxygen setting.
  5. Adjust oxygen percentage with DOWN or UP and confirm with SELECT.
  6. Continue with adjusting helium percentage and PO2 value.
  7. After pressing SELECT to confirm the PO2 value, press UP to move to the next diluent.
  8. Repeat steps 4 and 5 for each diluent.
  9. Press MODE to exit.

Open-circuit gases

As with closed-circuit gases, you must always define the correct oxygen and helium percentages of open-circuit gases (bailout gases) to ensure correct tissue and oxygen calculation.

Follow the same procedure as the CC gases to define your open-circuit gases under the OC Gases settings.

After entering values for Mix1, you can create additional mixes,Mix2 to Mix8. Each additional mix can be primary, secondary, or off. Mix1 is always set as a primary gas.

To minimize the risk of error during a dive, it is highly recommended that the mixes are set in the proper order. This means that as the mix number rises, so does oxygen content. This is the order they are usually used during the dive. Before a dive, only enable the mixes you actually have available and remember to check the set values to ensure they are correct.

The ascent time is calculated based on the assumption that you start the ascent profile immediately and all the primary gases are changed as soon as their maximum operating depth allows it. That is, using the gases that are set as primary, the most optimal ascent schedule for the moment is calculated.

To see the most pessimistic ascent schedule, that is, a schedule for the situation when gases are not changed at all, you can set the gases as secondary and the time it takes to finish the decompression using the current breathing gas is shown as the ascent time.

Showing the most pessimistic ascent schedule during a long dive may result in the ascent time no longer fitting the reserved field, and the dive watch displays '––'.

NOTE:

While setting the gases, notice that the calculated maximum operating depth is displayed in the upper field. You cannot change to this gas before you have ascended above this depth.

Setpoints

In CCR mode there are two setpoint values that you can set, low and high. Typically you do not need to modify the default setpoint values. However, you can change them as needed either in DM5 or under the CCR mode settings.

  • Low set point: 0.4 – 0.9 (default: 0.7)
  • High set point: 1.0 – 1.6 (default: 1.3)

To change set point values:

  1. While in CCR mode, keep DOWN pressed.
  2. Press UP to scroll to Setpoint and press SELECT.
  3. Press DOWN or UP to choose Low Setpoint and press SELECT.
  4. Press DOWN or UP to set value for PO2 and accept with SELECT.
  5. Repeat steps 2-4 for High Setpoint if necessary.
  6. Press MODE to exit.
Setpoint switching

You can use automatic or manual setpoint switching. The automatic low setpoint switch depth is 4.5 m (15 ft) by default, and the high setpoint switch depth is 21 m (70 ft).

The auto setpoint switching is off by default for the low setpoint and on for the high setpoint.

To modify setpoint switching:

  1. While in CCR mode, keep DOWN pressed.
  2. Press UP to scroll to Switch High and press SELECT.
  3. Press DOWN or UP to to toggle On/Off and press SELECT.
  4. Press DOWN or UP to set value for for Switch High in meters (m).
  5. Press SELECT to save
  6. Repeat steps 2-4 for Switch Low if necessary.
  7. Press MODE to exit.
Modify setpoints during a dive

The high and low setpoints or a custom (manual) set point can be adjusted during a dive.

To modify setpoints during a dive:

  1. While in CCR mode, keep UP pressed.
  2. Scroll to the setpoint you want to adjust with UP or DOWN.
  3. Press SELECT to enter the setting.
  4. Press DOWN or UP to adjust value.
  5. Press SELECT to save.
  6. Press MODE to exit.

Changing gases

In CCR dive mode, Suunto DX allows both setpoint and gas changes to enabled gas mixes during the dive.

To adjust the diluent during a dive:

  1. Keep UP pressed.
  2. Scroll through the settings with UP or DOWN to access the CC Diluent setting and press SELECT.
  3. Scroll through the diluent list with UP or DOWN and press SELECT to select a Diluent.

Enabled open-circuit gas changes are made in the same way and at the same time as the closed-circuit (CC) dive changes to an open-circuit (OC) dive. This feature is useful in bail-out situations.

Hyperoxic and hypoxic mixes

Suunto DX displays the text HYPER if the diluent gas PO2 at the current depth is over 1.6. The text HYPOX is displayed if the diluent gas PO2 at the current depth is less than 0.18.

Gauge mode

With Gauge mode, you can use Suunto DX as a bottom timer.

The timer in the center of the display shows dive time in minutes and seconds and activates at the start of the dive. The total running dive time, in minutes, is in the lower right corner.

The timer in the center of the display can be used as a stopwatch by pressing SELECT during the dive.

Pressing SELECT resets the main timer and adds a bookmark to the dive log. The previously-timed interval is displayed below the main timer.

gauge mode timer Dseries

Gauge mode has the following settings

Gauge mode is a bottom timer only and thus includes no decompression information or calculations.