Meridian...Meridian as a watch is the main time of day display. This is the display in which the...

®

Meridian

2 SCUBAPRO MERIDIAN

8. 2011 bz

Meridian diving CoMputer - designed by diversWelcome to SCUBAPRO dive computers and thank you for purchasing the Meridian. You are now the owner of an extraordinary partner for your dives. This manual provides you easy access to SCUBAPRO state of the art technology and Meridian’s key features and functions. Should you wish to know more about SCUBAPRO diving equipment, please visit our website www.scubapro.com.

Warning•Meridianhasadepthratingof120m/394ft.•If120misexceeded,--willbeshowninthedepthfieldandthedecompressionalgorithmdoesnot

calculatecorrectly.•Divingatoxygenpartialpressureshigher than1.6bar (corresponding toadepthof67m/220ft

whenbreathingcompressedair)isextremelydangerousandcouldleadtoseriousinjuryordeath.

Merdian dive instrument is a personal protective equipment in compliance with the essential safety requirements of the European Union directive 89/686/EEC. RINA SpA, Via Corsica 12, I-16128 Genoa, notified body no. 0474, have certified the conformity with the European Standard EN 13319:2000.

EN13319:2000 Diving accessories - Depth gauges and combined depth and time measuring devices - Functional and safety requirements, test methods. Any information on decompression obligation displayed by equipment covered by this standard is explicitly excluded from its scope.

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tabLe oF Contents

1. introduction to Meridian ....................................................................................... 61.1 Battery .................................................................................................... 6

2. Meridian as a watch ............................................................................................. 82.1.1 Setting the alarm clock ........................................................... 122.1.2 Setting the UTC ..................................................................... 122.1.3 Setting the time ...................................................................... 122.1.4 Set the 12/24h mode ............................................................. 132.1.5 Setting the date ..................................................................... 132.1.6 Setting the sound to “off ” (silent mode) .................................. 132.1.7 Checking the battery status ................................................... 142.1.8 Checking the device ID .......................................................... 15

2.1 Menus and functions ............................................................................. 162.1.1 Using the Stopwatch .............................................................. 172.1.2 Checking the Altitude ............................................................. 172.1.3 Planning a dive ....................................................................... 182.1.4 Reading the Logbook ............................................................. 192.1.5 Dive surface mode display ..................................................... 20

3. Meridian as a dive computer ............................................................................. 213.1 Settings at the dive mode ...................................................................... 21

3.1.1 Dive mode at surface ............................................................. 233.1.2 Surface interval counter .......................................................... 23

3.2 Gas settings .......................................................................................... 233.2.1 Set Gas 1 ............................................................................... 233.2.2 Set Gas d ............................................................................... 243.2.3 Nitrox reset time ..................................................................... 243.2.4 Workload settings (pulse limits) .............................................. 253.2.5 Desaturation reset .................................................................. 25

3.3 SCUBA settings .................................................................................... 253.3.1 Maximum dive depth alarm ................................................... 253.3.2 Maximum dive time alarm ...................................................... 263.3.3 Setting the Micro Bubble level ............................................... 263.3.4 Setting the Safety stop timer .................................................. 263.3.5 Setting the user preferred units .............................................. 263.3.6 Selecting the salt (ocean) or fresh water ................................. 273.3.7 Setting the Backlight on duration ........................................... 273.3.8 Setting audible attention signals on and off ............................ 273.3.9 Deactivating the water contacts ............................................. 28

3.4 APNEA Settings .................................................................................... 283.4.1 Setting the dual depth alarm .................................................. 283.4.2 Setting the depth incremental alarm ....................................... 293.4.3 Setting the dive time interval warning ..................................... 293.4.4 Setting the surface interval warning ........................................ 293.4.5 Setting the low Heart Rate limit alarm ..................................... 293.4.6 Setting the Ascent speed alarm ............................................. 303.4.7 Setting the water density ........................................................ 30

3.5 Algorithm selection ................................................................................ 31

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3.6 Diving with Meridian .............................................................................. 323.6.1 Display information ................................................................. 323.6.2 Display configuration during the dive ..................................... 33

3.7 Altitude diving ........................................................................................ 343.7.1 Altitude classes, altitude warning and no-fly time after a dive .. 343.7.2 Altitude and the decompression algorithm .............................. 353.7.3 Prohibited altitude .................................................................. 353.7.4 Decompression dives in mountain lakes ................................. 36

3.8 No-dive warning after a dive .................................................................. 363.9 SOS ...................................................................................................... 37

3.9.1 Desaturation reset .................................................................. 373.10 Diving with nitrox or with another decompression gas ........................... 37

3.10.1 Diving with two gas mixtures .................................................. 383.11 Warnings and alarms ............................................................................. 40

3.11.1 CNS O2 = 75% ....................................................................... 403.11.2 No-Stop time = 2 minutes ...................................................... 403.11.3 Entering decompression ........................................................ 413.11.4 Entering level stops ................................................................ 413.11.5 L0 no stop time = 2 minutes when diving an MB level ............ 413.11.6 Entering deco when diving an MB level .................................. 413.11.7 Ascent rate ........................................................................... 413.11.8 MOD/ppO2 ............................................................................ 423.11.9 CNS O2 = 100% ..................................................................... 423.11.10 Missed decompression stop .................................................. 433.11.11 Low battery ............................................................................ 433.11.12 Setting bookmarks ................................................................. 433.11.13 Safety stop timer .................................................................... 433.11.14 Activating the backlight .......................................................... 443.11.15 Diving with MB levels ............................................................. 443.11.16 Display information ................................................................. 453.11.17 Display of underlying L0 decompression information ............. 463.11.18 Cascading MB levels .............................................................. 463.11.19 Level stop ignored/MB level reduced ...................................... 463.11.20 PDI Stops .............................................................................. 46

3.12 GAUGE mode ....................................................................................... 473.13 APNEA mode ........................................................................................ 49

4. Meridian accessories ......................................................................................... 504.1 HR belt .................................................................................................. 504.2 Nylon arm strap ..................................................................................... 50

5. Meridian pC interface ......................................................................................... 515.1 Cradle .................................................................................................. 515.2 Introduction to SCUBAPRO LogTRAK ................................................... 51

5.2.1 Download dive profiles ........................................................... 515.2.2 Change warnings/settings of the Meridian and reading dive

computer info ......................................................................... 52

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6. taking care of Meridian ...................................................................................... 536.1 Technical information ............................................................................. 536.2 Maintenance ......................................................................................... 536.3 Replacing the battery in Meridian ......................................................... 546.4 Warranty ................................................................................................ 55

7. glossary ............................................................................................................... 56

8. index ..................................................................................................................... 58

1. introduction to Meridian

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1. introduction to Meridian

1. introduCtion to Meridian

The Meridian User Manual is divided into the following main sections.

1 introduction to Meridian. This section provides an overview of the Meridian dive computer and describes its operating modes and functions when on the surface.

2 Meridian as a watch. This section describes Meridian when it is used as a watch.

3 Meridian as a dive computer. This section describes all settings and functions of Meridian as a dive computer and takes you underwater with Meridian. It’s about everything Meridian can and will do to enhance your safety and fun underwater.

4 Meridian accessories. This section briefly describes the Meridian extras that can be purchased as additional options, to get the most from your dive computer in all diving conditions.

5 Meridian pC interface. This section is about personalization and customization. It describes how to change settings, to download and manage your logbook.

Meridian is a technologically-advanced instrument that can accompany you during your underwater adventures while providing you with accurate depth, time and decompression information. On the surface its size and good looks makes it an ideal everyday watch. With features such as wake-up alarm, stop watch, and altimeter, Meridian can handle almost every task in your daily activities.

The buttons allow you to operate functions, access menus and change settings while on the surface. During the dive buttons set bookmarks, show additional information on the dive computer screen and activate the backlight.

We hope you will enjoy getting to know your new dive computer and we wish you many wondrous dives with the Meridian.

1.1 Battery

Meridian uses a CR2032 lithium battery, available from your authorized SCUBAPRO dealer. To reduce the risk of fire or burns, follow the battery manufacturers recommendations when replacing, recycling or disposing the battery. Meridian will alert you when the battery is approaching a critical value by displaying the battery symbol. In addition, you can verify the status of the battery on the main menu.

When the battery symbol appears, this means that the battery is in fact low, although with some reserve remaining. In dive mode the backlight will not activate or work when the battery is low and the battery symbol is shown. If the battery symbol flashs the battery level is dangerously low and neither the backlight nor the alarm tones will be activated, and therefore diving

1. introduction to Meridian 1. introduction to Meridian

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is not recommended before changing the battery.

Battery symbol

WarningStarting a dive when the battery symbol isflashing can cause the dive computer to failduring the dive! Replace the battery beforeany diving activity if the flashing batterysymbolappears.When the ‘do not dive symbol’ appears withthebatterysymbol,Meridiancannotbeusedfordivingbeforereplacedwithanewbattery.

Donotdivesymbol

Please refer to chapter 2.1.7 Checking the battery status for details how to check your Meridian battery status.

WarningReplacing the battery requires opening theelectronic compartment of Meridian. Youmust take extreme care when performingthe battery change operation in order toensure the water seal of the watch. Failingto do so will cause Meridian to flood duringyour next dive and permanently damage thedivecomputer.DamagetoMeridianduetoanimproperbattery replacement is not coveredby warranty.We strongly recommend havingthebatterychangeoperationbecarriedoutbyyourauthorizedSCUBAPROdiveretailer.

See chapter 6.3 replacing the battery in Meridian for more information on how to replace the battery.

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2. Meridian as a watch

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Button LIGHT, Top Left : Short press = backlight

Button +/UP, Top Right: +/UP = adds numerical values, scrolls up in themenus

Button –/DOWN, Bottom Right:

–/DOWN = subtracts numerical values, scrolls downin the menus

Button SEL/ESC, Bottom Left:

• Short press = select,• Long press = escape (return to previous menu) or• cancel the setting

The diagram below shows the watch menu logic in a graphic form. The diving functions are described in detail in section 3 Meridian as a dive computer.

2. Meridian as a WatCh

Meridian is more than just a watch. It features:• a wake-up alarm-clock function• a stopwatch with lap time and 99 hours

run time• an altimeter for tracking excursions to

the mountains.• a thermometer

FNOTE: Considering that the metalhousing is a good heat conductor,the temperature reading will bewarmer than reality when wearingMeridiandirectlyonthewristexposedto your skin. This does not happenunderwaterasusually it iswornoverawetsuit.

The functions of the buttons when on the surface are summarized in the table below and explained in detail in the following sections.

LIGHT +/UP

–/DOWNSEL/ESC

2. Meridian as a watch 2. Meridian as a watch

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TIME & DATE

SET Soundoff

CHECKbattery state

Unit ID

SET alarmclock STOP watch

STOP watchfunction

SET time Planner Plannerpages

SET 12/24hmode LOG

Logbookpages

SET date DIVE mode

UTC Altitude meter

+/UP +/UP

+/UP

+/UP

+/UP

+/UP

+/UP

+/UP

SEL +/UP

+/UP

+/UP

+/UP

SEL

SEL

SEL

SEL Dive settings& menus

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The reference point for any description of Meridian as a watch is the main time of day display. This is the display in which the current time is shown in the middle row. The upper display row shows the date. For example the diagram below shows Saturday, 23rd of November and the time is one second past 10 o’clock.

24h mode

12h mode


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ClocksettingfunctionsBy pressing the SEL/ESC button from the main time and date display you will get into clock settings (marked dark at the graphics below).By pressing +/UP button you scroll to the next menu. By pressing SEL/ESC button

you may edit the settings and values on that current menu.

TIME & DATE

SET Soundoff

CHECKbattery state

Unit ID


SET time Planner

SET 12/24hmode LOG

SET date DIVE mode

UTC Altitude meter

+/UP +/UP

+/UP

+/UP

+/UP

+/UP

+/UP

+/UP

SEL +/UP

+/UP

+/UP

+/UP

+/UP

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2.1.1 Settingthealarmclock

Alarmoff

By pressing the SEL/ESC button the alarm time will start flashing. You can scroll the hours setting by pressing +/UP or –/DOWN buttons. By again pressing the SEL/ESC button the minutes will start flashing and by pressing +/UP or –/DOWN buttons you can scroll them.By again pressing the SEL/ESC button the state of alarm will start flashing and ‘on’ or ‘off’ can be selected by pressing +/UP or –/DOWN buttons. Pressing the SEL/ESC button again at the end will confirm the alarm time settings.

FNOTE: Setting the sound setting to ‘off’ does not affect the alarm clock. However, the intelligent battery stretching algorithm disables all warning tones when there are two or less dots remaining on the battery status display or when the battery symbol is flashing in another display.

2.1.2 SettingtheUTC

UTC setting will change the shown time compared to Greenwich 0-Meridian. This feature is practical when travelling through different time zones.By pressing SEL at UTC menu, the hours will start to flash. You may edit them with +/UP or –/DOWN buttons. By pressing SEL the minutes will start to flash and you may edit them with +/UP or –/DOWN buttons in 15 minutes increments. Activate the UTC setting by pressing SEL.

2.1.3 Settingthetime

Settingthecurrenttime

In the display above the current time is displayed on the menu. By pressing the SEL/ESC button, the time setting will be activated: hours start flashing and seconds will turn to 00. You may change the hours with +/UP or –/DOWN buttons. By pressing the SEL/ESC button the selection will change to minutes and you may now edit them. By pressing the SEL/ESC the new time setting will be saved.

FNOTE: seconds cannot be edited; they always start counting from 0.


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2.1.4 Setthe12/24hmode

24hourdisplay

By pressing the SEL/ESC button at the mode menu 24h starts flashing. With +/UP or –/DOWN buttons you may change between 24 hour or 12 hour format = am/pm displays. Pressing SEL/ESC will save the selection.

FNOTE: the 12 hour selection willchange the shown day format todisplaydateinthefollowingsequence:

Month.Date.Year. If you keep thewatch in the 24 hour format, youwill have the date displayed in thefollowingsequence:Date.Month.YearThis change also takes place in thewatch and in the dive computer logbook.

2.1.5 Settingthedate

When setting the date, by pressing the SEL/ESC button, the first digits will flash, indicating they can be changed by pressing +/UP or –/DOWN buttons (in 24h mode the first digit is days, in 12h mode the first digit

is the month). By pressing the SEL/ESC button the setting will be saved and move to the next digits. Again by pressing the SEL/ESC button the year digits after the dot will start flashing.

2.1.6 Settingthesoundto“off”(silentmode)

By pressing the SEL/ESC button the ‘on’ setting will start flashing at the bottom of the display. By pressing +/UP or –/DOWN buttons you may select ‘on’ or ‘off’ for the Meridian silent mode for alarms and button tones. The sound off selection is protected with a code.

WarningThe Sound ‘off’ selection will disable allaudibledivemodealarmsandwarnings.Thisispotentiallydangerous.

FNOTE: the only exception to the silent operation is the alarm clock. It will remain activated even if the main setting is: sound off.

To turn off the sound a code must be entered into the dive computer to activate the change. The unlock code for ‘sound off’ is 313. When the sound off option has been selected the first digit starts flashing. By pressing +/UP or –/DOWN buttons the code number can be changed and by pressing the SEL/ESC button the code number will be stored.

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Batterystatusdisplayinbattery

mode

Displayinothermodes

Batterystatus Functionlimitations

ooooo Fresh battery none

oooo Battery ok for diving none

ooo Battery ok for diving none

oo change Battery symbol Weak battery, change battery

Backlight not operat-ing

o change Flashing battery sym-bol, no dive symbol

Completely used bat-tery, must change

Alarms and Backlight not operating, diving not recommended

None, change Flashing battery sym-bol, no dive symbol

Completely used battery, must change, watch may reset at

any time and remain off

Diving mode not allowed, only watch may be

active

2.1.7 Checkingthebatterystatus

Battery status

The battery status menu displays how much energy is left in the CR2032 battery. A brand new battery shows 5 dots.

Meridian is periodically measures the battery status and you can manually trigger this display by pressing the SEL/ESC button in the battery status menu.

The intelligent battery algorithm will limit some functions when the battery is close to running out. See the table below for battery status and function details.


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2.1.8 CheckingthedeviceID

Each Meridian watch has a specific, individual ID number. The 10 digit ID number is shown in this menu.

FNOTE: The battery capacity andvoltage at the end of the batterylifetimemayvarydependingonbatterymanufacturers. Generally, operationat low temperatures decreases thebatterycapacity.Therefore,whenthebattery indicatordropsbelow3dots,changethebatterybeforemakinganydives.

Change the battery before the next dive

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2.1 Menusandfunctions

By simply pressing buttons +/UP or –/DOWN from the time of day display you can scroll through the various menus in Meridian. The diagram below shows the sequence of the menus. Note that when you first reach a menu, you are “outside” of it. You must SEL/ESC button to enter the actual menu.

TIME & DATE

SET Soundoff

CHECKbattery state

Unit ID


SET time Planner

SET 12/24hmode LOG

SET date DIVE mode

UTC Altitude meter

+/UP +/UP

+/UP

+/UP

+/UP

+/UP

+/UP

+/UP

SEL +/UP

+/UP

+/UP

+/UP


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2.1.1 UsingtheStopwatch

The first menu from the time of day display is STOP (watch). By pressing SEL/ESC button the stopwatch will be activated.

In the first display the stopwatch shows the status, which can be stop, run or lap. When activating the stopwatch for the first time the display will be as shown above.

Press +/UP button and the stopwatch starts counting showing: run. Press +/UP button again to stop the counting. The counted time will stay on the display.Stopwatch will reset the counted time when +/UP button is pressed and held.

The laps can be marked by pressing –/DOWN button when stopwatch is counting. By doing so the display will freeze for 5 seconds and Meridian shows the lap time.

Counting will continue automatically and the lap counter will show the number of laps at the bottom of the screen.

By pressing SEL/ESC button you can exit the stopwatch and return to the stopwatch menu.

FNOTE: You can leave the stopwatchactively counting or you can leavethestopped timeon thedisplay.Thestatuswillbestoredinamemorythatallowsyoutocontinuefromthesamedisplaythenexttime.

2.1.2 CheckingtheAltitude

Current Altitude Class

Altitude Temperature

On the altitude menu, the current altitude is calculated from the barometric pressure. The current altitude, the Altitude Class and the temperature are shown.

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FNOTE: barometric pressure is avariable, changing with weather andatmospheric pressure at a specificelevation.DivealgorithmusesAltitudeClasses which are directly derivedfromthebarometricpressure.Altitudeiscountedfromthecurrentbarometricpressureand it is thereforea relativevalue.

The altitude can be adjusted when current elevation is known by pressing the SEL/ESC button. The altitude value will start flashing. By pressing +/UP or –/DOWN buttons the value can be adjusted in 10m/50feet increments. Adjusting the altitude elevation has no effect on Altitude Class.

FNOTE: Different altitude/temperaturemeasurement combinations such asm&˚C, Ft&˚C, m&˚F or Ft&˚F can beselectedfromthedivemodemenuin:Units.

2.1.3 Planningadive

You can plan your next dive based on your body’s nitrogen saturation. The planner also uses the following information:1. Selected oxygen concentration and

active tanks2. Selected water type3. Selected microbubble level4. Water temperature of the most recent

dive5. Altitude class6. Status of saturation at the time the plan-

ner is started7. A normal workload of the diver and

observance of the prescribed ascent rates.

By pressing SEL/ESC button at the planner menu you will get into the planner directly or to the surface interval setting (repetitive dive).

FNOTE:WhenMeridianisinGAUGEorAPNEAmodesthePlannerisdisabledand Planner OFF is shown in thismenu.

Prohibited Altitude Class

Surface interval

Surface intervalFor repetitive dives enter the surface interval: By pressing the +/UP or –/DOWN buttons the surface interval can be adjusted in 15 minutes increments. The prohibited altitude is shown on the top row and by increasing the surface interval the allowed limit will get to maximum (level 4).In case Meridian is displaying the no-dive warning, the duration of the warning itself is displayed as recommended surface interval for planning purposes (rounded up to the nearest fifteen-minute increment).


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Depth No-stop time

O2 mix

When surface interval is given or if you have no remaining desaturation left, the planner will start flashing the depth. By pressing + or – you can set the depth in 3m/10feet increments.The No-stop time is shown for that depth at the middle row.The gas O2 mix is shown at the bottom row until the 1% CNS for the planned depth has been reached. After that the planner shows the CNS% at bottom row.Minimum depth for planning is 9m/30feet or MOD of the Gas d (when active).The planner allows only depths according to maximum ppO2 given to the Gas 1. The gas oxygen mix and maximum ppO2 settings are given at the dive mode menu: SET GAS.

WarningIf you have set ppO2max to OFF, the plannerwill allow depths up to a maximum of120m/394ft. Air/nitrox dives with high ppO2are extremely dangerous and can lead todeath.BeawarethatexposurestohighppO2willleadCNSclockvaluetoexceedmaximumrecommended100%.

If Gas 1 MOD is shallower than 9m/30feet, planning is not allowed and information LO ppO2 is shown.

FNOTE: The dive planner considersall programmed gas mixtures

when computing no-stop times ordecompressionschedules.

By pressing SEL/ESC for planned depth the dive time appears at top row. Start point (minimum now) is the no decompression time. By pressing +/UP or –/DOWN buttons you may change the time in 1 minute increments. When no decompression time is exceeded the planner gives decompression time at the middle row.

By pressing SEL/ESC the planner will exit and you will return to the main menu.

2.1.4 ReadingtheLogbook

You can check the main information about your dives from the logbook by pressing SEL/ESC in the log menu.The first page shown is the dive history.

Deepest dive Longest dive

Cumulative bottom time

Number of dives

This dive computer history shown above, the deepest dive is 39.9 meters and the longest dive time is 58 minutes. In total,

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3. Meridian as a dive computer

6 hours of diving and 22 dives have been done with this Meridian.

By pressing +/UP or –/DOWN buttons you can scroll the dives in the memory. In SCUBA mode there is a main page showing maximum depth, dive time, dive date, log number and used Gas 1 oxygen mix.

Max depth Dive time

Dive number Dive dateO2 mix

If the dive has been done in GAUGE or APNEA modes, the main page has GA or AP instead of O2% at the bottom row.

By pressing SEL/ESC you will select the dive and get to the sub display. The information on the display varies depending on the mode of dive:• Scuba mode: Minimum temperature,

dive start time and average heart rate (if enabled).

• APNEA mode: The bottom row will show the maximum ascent rate.

• GAUGE mode: The bottom row will show the average depth.

2.1.5 Divesurfacemodedisplay

This display is the starting point of dive functions and sub menus related to underwater options. This is described in detail in the following section 3 Meridian as a dive computer.

2. Meridian as a watch 3. Meridian as a dive computer

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3. Meridian as a dive CoMputer

Meridian is a full-featured dive computer, capable of multi-gas decompression calculations, ascent rate calculations and warnings. The logbook can store 50 hours of dive profiles with a 4 second sampling rate. While diving, it displays depth, dive time, decompression status, water temperature and much more. On the surface, after a dive, it displays remaining desaturation time, no-fly time, surface interval and prohibited Altitude Classes are shown in addition to the watch functions.

3.1 Settingsatthedivemode

When Meridian is in surface mode, you can access various menus dedicated to diving and customize various settings.

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DIVE mode(SCUBA/APNEA/GAUGE)

Surface Interval(only when desat left)

ALGORITHM select:SCUBA/APNEA/GAUGE

SET GAS 1

+/UP

+/UP

SEL

SEL

SEL

SEL

SET GAS D+/UP

Nitrox reset time+/UP

SET HR limits+/UP

Desaturation reset+/UP

SET GAS

Max Depth alarm

+/UP

+/UP

+/UP

+/UP

Max Time alarm+/UP

MB level+/UP

Safety stop timer+/UP

Units

+/UP

Salt water selection+/UP

Back light duration time+/UP

Attention beeps+/UP

+/UP

SET SCUBA

Dual Depth alarm+/UP

Depth Increment alarm+/UP

Dive interval alarm+/UP

Surface interval alarm+/UP

Low HR alarm

+/UP

Ascent speed alarm+/UP

Water density+/UP

SET APNEA

Water contact activation

3. Meridian as a dive computer 3. Meridian as a dive computer

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The dive computer functions of Meridian on the surface include, among others, setting the oxygen concentration for nitrox diving, setting the MB level of the decompression algorithm, setting various warnings and personal preferences,. To reach any of these functions, Meridian must be in Dive surface mode display. This can be reached pressing the –/DOWN button once from the main time and date display, until text SCUBA, GAUGE or APNEA is shown (after a dive, more information may appear – this is described later in this chapter).

3.1.1 Divemodeatsurface

When you have not been diving with your Meridian for a while (no desaturation left) the dive mode may appear as shown below:

However in SCUBA mode after a dive, the display may appear as shown below:

From here (SCUBA mode, after a dive), by pressing the SEL/ESC button and scrolling with the +/UP or –/DOWN buttons, you can access a loop of additional menus related to diving, which are: surface interval, set

gas, set scuba, set apnea and algorithm select.

3.1.2 Surfaceintervalcounter

After a dive the Meridian shows the surface interval from the latest dive. The surface interval counter counts until desaturation is complete. After the desaturation is complete this menu disappears.The no-fly time is shown at the upper row on the right corner in hours.

No-fly time

Surface interval

3.2 Gassettings

3.2.1 SetGas1

You may use your Meridian with all nitrox mixes from Air to pure oxygen. By pressing the SEL/ESC button in this display the oxygen mix of Gas 1 starts flashing. By pressing the +/UP or –/DOWN button you may scroll the value from 21 up to 100%.

WarningDivingwithappO2higherthan1.4isdangerousand may lead to unconsciousness, drowninganddeath.

By pressing SEL/ESC the maximum partial pressure of oxygen (ppO2 max) starts flashing. By pressing the +/UP or –/DOWN button you may select the value from 1.00 bar up to 1.60 bar.

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FNOTE:ppO2isfixedto1.60barwhenselected oxygen fraction is 80% orhigher.

Maximum partial pressure of oxygen (ppO2 max)

Maximum Operating Depth (MOD)

O2 mix of Gas 1

It is possible to disable the MOD setting (- - shown at the field), but this requires the security code 313 from the user.

WarningDivingdeeperthantheMODisdangerousandmayleadtoseriousinjuryordeath.

By pressing the SEL/ESC button the user will accept the given value.

3.2.2 SetGasd

When you are planning to make an extended no-stop dive or decompression dive with another mix for accelerated decompression you may set the second gas to active. You may select the Gas d fraction and ppO2 combination so that the MOD is 3m/10ft deeper than with Gas 1.

By pressing SEL/ESC at this display the oxygen fraction starts to flash. By pressing the +/UP or –/DOWN button you may scroll the value. After accepting it by pressing the SEL/ESC button the maximum partial pressure of oxygen (ppO2 max) value starts to flash. By pressing +/UP or -/DOWN button the value may be selected from 1.00 bar up to 1.60 bar in 0.05 bar increments.

Maximum partial pressure of oxygen (ppO2 max)

Gas d disabled

Gas d is disabled when - - is shown at %O2 fractions field.

3.2.3 Nitroxresettime

If you are generally diving with one gas or air only and want to return to this setting after occasional nitrox or multi gas dives, you can preset a default time when your Meridian will reset to air and disable the Gas d.

Gas reset time is disabled when - - h is shown.


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3.2.4 Workloadsettings(pulselimits)

By pressing SEL/ESC button in this menu the Heart Rate (HR) high value starts to flash. By pressing the +/UP or –/DOWN button the value can be changed. By pressing SEL/ESC button the low value starts to flash. By pressing +/- the value can be changed. By pressing SEL/ESC again the mode starts to flash. Possible selections are pulse or off. By pressing SEL/ESC the mode will be entered.

When Pulse is selected then the diving algorithm uses it as an input for the workload. When Off is selected, then the workload is disabled.

Heart rate high value

Heart rate low value

Pulse

3.2.5 Desaturationreset

WarningResettingdesaturationwilleffectcalculationsofthealgorithmandthismayleadtoseriousinjury or death. Do not reset desaturationwithoutasolidpurpose.

When Meridian is still counting down the desaturation, some menu changes are not possible. In case the user decides to reset the desaturation, the safety code 313 must be entered. This procedure secures unwanted resetting and the desaturation reset will be stored in the memory on the next dive log the desaturation symbol will be shown.

3.3 SCUBAsettings

A set of SCUBA related selections are grouped in this menu.

By pressing the SEL/ESC button the following menu’s can be scrolled down.

3.3.1 Maximumdivedepthalarm

By pressing SEL/ESC button in this menu the depth value starts to flash. By pressing the +/UP or –/DOWN button the value can be selected between 5 and 100 meters (20 to 330 feet) in 1m (5ft) increments.

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By pressing SEL/ESC button the function starts to flash and you may select On or Off by pressing the +/UP or –/DOWN button. The selection is confirmed by pressing SEL/ESC button.

Alarm depth

Status

3.3.2 Maximumdivetimealarm

By pressing SEL/ESC button in this menu the time value starts to flash. By pressing the +/UP or –/DOWN button the value can be selected between 5 and 195 minutes in 1 minute increments. By pressing SEL/ESC button the function starts to flash and you may select On or Off by pressing the +/UP or –/DOWN button. The selection is confirmed by pressing SEL/ESC button.

Alarm time

Status

3.3.3 SettingtheMicroBubblelevel

By pressing SEL/ESC button in this menu the Micro Bubble level starts to flash. By pressing the +/UP or –/DOWN button you may select personal settings from L0 up to

L5. L5 is the most conservative setting. The selection is confirmed by pressing SEL/ESC button.

Micro Bubble level

FNOTE:moreaboutdivingwiththeMBlevels,readchapter:Diving with MB levels.

3.3.4 SettingtheSafetystoptimer

Meridian safety stop timer starts automatically when the depth at the end of the dive becomes less than 5m/15ft and all decompression or MB stops have been accomplished.

By pressing SEL/ESC button at this menu the number at the bottom row will start flashing. By pressing the +/UP or –/DOWN button the value can be set between 1 to 5 minutes or to Off.

Duration of the safety stop

3.3.5 Settingtheuserpreferredunits

The user may select between depth and temperature unit combinations. The effect


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takes place in dive mode, in the log book, alarm settings, altitude settings etc.

By pressing SEL/ESC button in this menu the style of units field value starts to flash. By the +/UP or –/DOWN button the value can be changed between meters/feet. By pressing SEL/ESC button the temperature field starts to flash. Again by pressing +/- the value may be changed. By pressing SEL/ESC button both unit settings will be confirmed.

3.3.6 Selectingthesalt(ocean)orfreshwater

Meridian measures a pressure and converts depth from it by using the water density as a constant. 10m/33ft depth at salt water corresponds approximately to 10.3m/34ft at fresh water.

By pressing SEL/ESC button at this menu the on/off field at the bottom row starts to flash. You may scroll between these two settings and confirm by pressing SEL/ESC button.

3.3.7 SettingtheBacklightonduration

By pressing SEL/ESC button on this menu the backlight duration field at bottom row starts flashing. By pressing the +/UP or –/DOWN button you may scroll between user presettable on time from 4 up to 60 seconds.

Status Backlight duration

3.3.8 Settingaudibleattentionsignalsonandoff

With this option you can switch off the audible attention signals only (the audible alarms remain active). By pressing SEL/ESC button on this menu the on/off field at the bottom row starts flashing. By pressing the +/UP or –/DOWN button you may select between audible attention signals On or Off. You may confirm the selection by pressing SEL/ESC button again.

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3.3.9 Deactivatingthewatercontacts

WarningIf you chose the option “Water contactsoff”, Meridian will turn on with a delay ofup to 1 minute into the dive.This will affectfunctioningofthedivecomputer.Make sure the Meridian is on the surfacemodebeforestartingthedive.

By pressing SEL/ESC button on this menu the on/off field at the bottom row starts flashing. By pressing the +/UP or –/DOWN button you may switch between active or inactive water contacts. You may confirm the selection by pressing SEL/ESC button again.

FNOTE: With inactive water contactyou prevent Meridian from switchingtodivereadymodewhenyourskinorsurface moisture activates the watercontact.

3.4 APNEASettings

APNEA diving related selections are grouped in this menu.

By pressing the SEL/ESC button the following menu’s can be accessed.

3.4.1 Settingthedualdepthalarm

With this alarm you can set two independent depth alarms. By pressing the SEL/ESC button at this menu the first depth starts flashing. By pressing the +/UP or –/DOWN button you may select the first depth alarm from 5 to 100 meters (20..330 feet). By pressing SEL/ESC the first value is confirmed and the second alarm starts flashing. Like the first, by pressing the +/UP or –/DOWN button the second alarm may be set from 5 to 100 meters.

First alarm depth Second alarm depth

Status

FNOTE: The first alarm is shortsequenceforattentionandthesecondalarmiscontinuous.Bysettingthefirstalarmdeeper than thesecond, itwill


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be masked by the continuous alarmandyoucannothearthefirstone.

3.4.2 Settingthedepthincrementalalarm

With this alarm you can set repetitive depth alarms at given depth increments. By pressing the SEL/ESC button in this menu the incremental alarm depth starts to flash. By pressing the +/UP or –/DOWN button you may select the alarm value from 5 to 100 meters (20..330 feet). By pressing SEL/ESC button the alarm value will be confirmed and the function at the bottom row starts flashing. By pressing the +/UP or –/DOWN button you may select the direction for the depth incremental alarm: off, dn (down), up or both.

Depth increment

Status

3.4.3 Settingthedivetimeintervalwarning

You can set a time warning that repeats on given intervals. By pressing SEL/ESC button at this menu (SurF) the dive time interval time starts to flash. By pressing +/- you can select the interval from 15 seconds up to 10 minutes. By pressing SEL/ESC button the function starts to flash and you may select to enable or disable by choosing on/off with the +/UP and –/DOWN button. By pressing SEL/ESC again the selection will be confirmed.

Dive time interval

Status

3.4.4 Settingthesurfaceintervalwarning

You can set a time for recovery or start time for repetitive dive when training against given tables. By pressing SEL/ESC button at this menu the surface interval time starts to flash. By pressing +/- you can select the interval from 15 seconds up to 10 minutes. By pressing SEL/ESC button the function starts to flash and you may select to enable or disable by setting on/off with the +/UP or –/DOWN button. By pressing SEL/ESC again the selection will be confirmed.

Surface interval

Status

3.4.5 SettingthelowHeartRatelimitalarm

In APNEA diving a low heart rate is a key for low oxygen consumption and therefore for longer dives. However, an extremely low pulse at depth may lead to loss of awareness and is dangerous.

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By pressing the SEL/ESC button at the PULSE menu the low heart rate value starts to flash. By pressing the +/UP or –/DOWN button you can set the value from 25 to 100 beats per minute. By pressing SEL/ESC button the value will be confirmed and function activation starts flashing. By pressing +/- you may select between on/off. By pressing SEL/ESC button the alarm will be confirmed.

Example: The HR alarm goes off if the heart rate reaches 40 or less beats per minute

Status

3.4.6 SettingtheAscentspeedalarm

With this alarm you can set ascent speed alarm. By pressing SEL/ESC at this menu (SPEEd) the ascend speed starts to flash. By pressing the +/UP or –/DOWN button you may select the value from 0.1 to 5.0 meters/second (1..15 feet/second). By pressing SEL/ESC the value will be confirmed and the function starts flashing. By pressing +/- you may select if alarm will be active by setting on/off. By pressing SEL/ESC the selection will be confirmed.

3.4.7 Settingthewaterdensity

At APNEA diving the exact depth is very important value. For the most accurate reading you must select the correct density of the water. Density depends on water temperature and salinity (salt content).

Some approximated densities at 20˚C/68˚F water:

• Average Ocean water has approximately 1025 gram/liter (59878 Grain/gallon).

• Mediterranean Sea has approximately 1027 gram/liter (59995 Grains/gallon).

• Red Sea has approximately 1029 gram/liter (60112 Grains/gallon).

• Black Sea has approximately 1012 gram/liter (59119 Grains/gallon).

• Baltic Sea has approximately 1004 gram/liter (58652 Grains/gallon).

• Fresh water (lake/quarry) has density approximately 1000 gram/liter (58417 Grains/gallon).

By pressing SEL/ESC at this menu (WAtEr) the water density value starts to flash. By pressing the +/UP or –/DOWN button you


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may change the value between 1000 and 1050 gram/liter (58417..61339 Grains/gallon). By pressing the SEL/ESC button the value is confirmed.

Water density

3.5 Algorithmselection

You may select your Meridian operation mode between SCUBA, GAUGE and APNEA modes.

When Meridian has not been submerged for a while the display will appear as follows:

By pressing the SEL/ESC button at this menu the mode starts to flash. By pressing the +/UP or –/DOWN button you may select between SCUBA, GAUGE and APNEA modes. Pressing the SEL/ESC button will confirm the selection.

since the gauge and apnea modes are not tracking the tissue saturation, there is a 48 h locking interval after the last dive in gauge or apnea mode before change to a sCuba mode is possible.

Meridian shown below has been dived in GAUGE mode and the NO CHANGE lock is still on for another 4 hours.

From the last SCUBA dive the change to GAUGE or to APNEA mode is possible only after the desaturation time has elapsed.

If you decide to change between modes before the 48 h interval or full desaturation you must go to the desaturation reset menu and make a manual desaturation reset.

WarningChanging ALGO with remaining saturationcouldleadtoinjuryordeath.

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3.6 DivingwithMeridian

The functions of the buttons during diving are summarized in the table below.

Note that Meridian can be set to three dive modes: SCUBA, APNEA and GAUGE. Due to the operation differences also buttons have different functions in each mode.

LIGHT (Left upper button)

• Short press = backlight,• Long press = bookmark

+/UP (Right upper button)

• Short press = alternative display data• Short press in APNEA mode = switch between HR and ASC speed

on display• Short press in GAUGE mode = alternative display data• Long press in GAUGE mode = reset average depth counter

-/DOWN (Right lower button)

• Short press = reset safety stop timer• Long press in APNEA mode = manual start and end the dive• Short press in GAUGE mode = start/stop timer

SEL/ESC (Left lower button)

• Long press = select manual gas switch• Short press (after long) = enter manual gas switch

3.6.1 Displayinformation

Upon immersion, Meridian will automatically start to monitor the dive regardless of what state it was in prior to the immersion. Details on the information displayed can be found in the next sections.

The dive time is displayed in minutes. If during the dive you ascend to the surface, the time spent on the surface will only be counted if you descend again below 0.8m/3ft within 5 minutes. This allows for brief periods of orientation. While on the surface, the time will not show as progressing but it is running in the background. As soon as you submerge, the time will resume, including the time spent on the surface. If you spend more than 5 minutes at depth shallower than 0.8m/3ft, the dive will be considered ended, the logbook closed and a subsequent immersion would cause the dive time to start again from zero.

Maximum displayed time is 999 minutes. For dives longer than that, the dive time starts again from 0 minutes.

Current depth Dive time

Max depth No-stop time

Divedisplaylimits(mertic)


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Current depth Dive time

Max depth No-stop time

Divedisplaylimits(imperial)

Depth: the depth is given in 10cm resolution when metric mode. When the depth is displayed in feet, the resolution is always 1 foot. At a depth shallower than 0.8m/3ft, the display shows --. Maximum possible depth is 120m/394ft.

No-stop time: calculated in real time and updated every 4 seconds. Maximum displayed no-stop times is 99 minutes.

WarningDuring all dives, perform a safety stopbetween3and5meters/10and15feetfor3to5minutes,even ifnodecompressionstopisrequired.

Temperature: Meridian displays the water temperature during the dive and the air temperature on the surface. However, the skin temperature influences the measurement when worn at the wrist.

Decompression information: when Meridian calculates the need for a mandatory decompression stop, it shows you how long and how deep your deepest stop is. It also gives you the total ascent time. Stops deeper than 27m/90ft and total ascent times longer than 99 minutes are shown as “- - “.

Decompression information at MB L0: if you are diving with an MB level different than MB L0, you can ask Meridian to show you the decompression information pertinent to the underlying MB L0 calculation. For more

information on MB levels, please refer to chapter 3.11.15 diving with Mb levels.

3.6.2 Displayconfigurationduringthedive

Throughout the dive, Meridian displays the current depth (upper left corner), the elapsed dive time (upper right corner) and the no-stop or decompression information (middle row).

In addition, Meridian utilizes the lower row to display additional information regarding the dive. By pressing +/UP button will show, in sequence:

1. PDIS depth (when pending)2. Maximum depth (only if 1m/3ft ascent

detected)2. Water temperature3. Heart rate (if activated)4. O2 %

a. MOD of the active gas (if Gas d enabled)

b. If Gas 1 active then bail out info using only Gas 1 at the middle row

c. Active MB level

d. No-stop or decompression information at L0 (displayed in middle row, only if diving with an MB level other than L0)

5. CNS % if greater than 1%6. Time of the day in the middle row

(temperature at bottom row)

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3.7 Altitudediving

3.7.1 Altitudeclasses,altitudewarningandno-flytimeafteradive

Going to altitude is in a way similar to starting an ascent from a dive: you expose your body to a lower partial pressure of nitrogen and consequently you start offgassing. After a dive, given the higher nitrogen loading in your body, even reaching an otherwise negligible altitude can potentially cause decompression sickness. Consequently, Meridian constantly monitors the ambient pressure and uses it to evaluate your nitrogen loading and offgassing. If Meridian notices a drop in ambient pressure not compatible with your current nitrogen loading, it will activate a warning to alert you of the potentially dangerous situation.

If you have remaining desaturation on Meridian, you can view the current altitude and the prohibited altitude by pressing the –/DOWN button from the main time display. In the top left corner, Meridian will display two numbers: the left number represents the current altitude, whereas the right number represents the prohibited altitude (the altitude which Meridian has computed to be incompatible with your current nitrogen saturation levels). Altitude here is given in classes from 0 up to 4. Please read chapter 3.7.2 altitude and the decompression algorithm for more details on this.


Prohibited Altitude Class

By pressing SEL/ESC button the next display will be shown:

Time since the last dive (interval)

No-fly time and symbol

Oxygen toxicity

In the top right corner Meridian shows the no-fly time and the no FLy symbol. The no-fly time is the time during which an exposure to the reduced pressure inside the cabin of an airplane could cause decompression sickness, as calculated by the decompression model in the dive computer.

In the top left Int is displayed (the time since the last dive) and in the middle row the time is counting.

In the bottom row the Oxygen toxicity (CNS O2) is shown in % values.

After the full desaturation the interval display disappears and the Gas setting menu is shown directly.


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WarningFlying while Meridian displays the NO FLYsymbolcanresultinseriousinjuryordeath.

3.7.2 Altitudeandthedecompressionalgorithm

Atmospheric pressure is a function of altitude and of weather conditions. This is an important aspect to consider for diving, because the atmospheric pressure

surrounding you has an influence on ongassing and offgassing of nitrogen. Above a certain altitude, the decompression algorithm has to change in order to account for the effect of the change in atmospheric pressure.

Meridian divides the possible altitude range in 5 classes that are illustrated in the illustration below:

ElevationAltitude Class

Barometric switch point

Dive Computer

mode

4000 m13120 ft

C4 610 mbar8.85 psi

GAUGE(no deco

data)

3000 m9840 ft

C3 725 mbar10.51 psi

SCUBA

2000 m6560 ft


SCUBA

1000 m3280 ft


SCUBA

0 m0 ft

C0 SCUBA

The Altitude Classes are defined in terms of approximate elevations because the effect of weather conditions can make the pressure switch point occur at different levels.

WarningAt Altitude Class 4, Meridian functions inGAUGEmodeonly(automaticswitchfromdivecomputermode).

FNOTE: You can check your currentAltitude Class and elevation byactivating thealtitudemeter.Refer tochapter Checking the Altitude onhowtodoso.

FNOTE: Meridian monitors thealtitude automatically: it monitorsthe atmospheric pressure every60secondsandifasufficientdropinpressureisdetected,thefollowingwilloccuritdoesthefollowing:

•AnewAltitudeClasswillbeindicated

and if applicable, the prohibitedAltitudeClasstoo;

•Thedesaturationtimewillbeindicated,whichinthiscaseisanadaptationtothenewambientpressure.Ifadiveisstarted during this adaptation time,Meridianconsidersitarepetitivedive,sincethebodyhasresidualnitrogen.

3.7.3 Prohibitedaltitude

Increasing altitude, as well as flying after diving, exposes your body to a reduced ambient pressure. In a way similar to the no-fly time, Meridian advises you as to which Altitude Classes are safe after a dive and which are not. For example, if you must drive over a mountain pass to return home after a dive, it can be quite important to have this information.

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Ascent to Altitude Class 4 prohibited

In the example above, the diver is presently at Altitude Class 2 and should not reach altitudes of class 4 (prohibited Altitude Class).

Meridian has an audible altitude warning: if you were to reach an altitude, that according to Meridian, is incompatible with your current residual nitrogen levels, it will warn you with an altitude warning.

3.7.4 Decompressiondivesinmountainlakes

In order to assure optimal decompression even at higher altitudes, the 3m/10ft decompression stage is divided into a 4m/13ft stage and a 2m/7ft stage in Altitude Class 1, 2 and 3.

If atmospheric pressure is below 610mbar (altitude higher than 4000m/13300ft), no decompression calculation is carried out by Meridian (automatic GAUGE mode). In addition, the dive planner is not available in this altitude class.

3.8 No-divewarningafteradive

If Meridian detects a situation of increased risk (due to the potential microbubble accumulation from previous dives or a CNS O2 level above 40%), the no dive symbol will appear on the display to advise you against performing another immediate dive right away. The suggested time interval that you should wait prior to diving is shown on the dive mode display.

No-dive warning

WarningIf the “no-dive” warning is visible duringthe surface interval, the diver should notundertakeanotherdive.

If the warning is prompted by microbubble accumulation (as opposed to CNS O2 over 40%) and you dive anyway, you will have shorter no-stop times or longer decompression times. Moreover, the duration of the microbubble warning at the end of the dive can increase considerably.


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3.9 SOS

If you stay above a depth of 0.8m/3ft for more than 3 minutes without observing a prescribed decompression stop, Meridian will switch into sos mode. Once in sos mode Meridian will lock up and will be inoperable as a dive computer for 24 hours. If it is used for diving within the 24hours of an sos lock, it will automatically switch to GAUGE mode and provide no decompression information.

Warning•Violating a mandatory decompression

obligation may result in serious injury ordeath.

•Seriousinjuryordeathmayresultifadiverdoesnotseek immediate treatmentshouldany signs or symptoms of decompressionsicknessoccurafteradive.

•Do not dive to treat symptoms ofdecompressionsickness.

•Do not dive when the dive computer is inSOSmode.

SOS

The display shows the same information as in presence of desaturation, but at the lowest row SOS is displayed.

3.9.1 Desaturationreset

Meridian allows you to reset the desaturation in the dive computer. Any tissue saturation information from a recent dive will be reset to zero and the dive computer treats the next dive as a non-repetitive dive. This is useful when the dive computer is loaned to

another diver who has not dived in the last 48 hours.

FNOTE: After a desaturation reset thechangebetweenthemodes:GAUGE,APNEA and SCUBA are possibleimmediately. However, since theGAUGE and APNEA modes are nottracking your tissuenitrogen loading,it is recommended to keep the initialintervalsbetweenchangesonmodes.

WarningDiving after having reset the desaturationis extremely dangerous and is very likely tocauseseriousinjuryordeath.Donotresetthedesaturationunlessyouhaveavalidreasontodoso.

FNOTE: Removing and replacing thebatterywillnotresetthedesaturation.Meridian stores tissue saturationinformation in non-volatile memory.For the time during which the divecomputer is without battery, thedesaturationcalculation is frozenandresumesfromwhere ithad leftoffassoonasanewbatteryisinstalled.

3.10 Divingwithnitroxorwithanotherdecompressiongas

Nitrox is the term used to describe breathing gases made of oxygen-nitrogen mixes with oxygen percentage higher than 21% (air). Because Nitrox contains less nitrogen than air, there is less nitrogen loading on the diver’s body at the same depth as compared to breathing air.

However, the increase in oxygen concentration in Nitrox implies an increase in oxygen partial pressure in the breathing mix at the same depth. At higher than atmospheric partial pressures, oxygen can have toxic effects on the human body. These can be lumped into two categories:Sudden effects due to oxygen partial pressure over 1.4bar. These are not related to the length of the exposure to high partial

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pressure oxygen, and can vary in terms of the exact level of partial pressure they happen at. It is commonly accepted that partial pressures up to 1.4 bar are tolerable, and several training agencies advocate maximum oxygen partial pressures up to 1.6 bar.

Long exposure effects to oxygen partial pressures over 0.5 bar due to repeated and/or long dives. These can affect the central nervous system, cause damage to lungs or to other vital organs. Long exposures can be divided to more severe Central Nervous System effects and less dangerous long term Pulmonary Toxicity effects.

Meridian treats high ppO2 and long exposure effects in the following ways:

Against sudden effects: Meridian has an MOD alarm set for a user-defined ppO2max. As you enter the oxygen concentration for the dive, Meridian shows you the corresponding MOD for the defined ppO2max. The default value of ppO2max from the factory is 1.4bar. This can be adjusted to your preference between 1.0 and 1.6bar. It can also be turned OFF. Please refer to chapter 3.2 gas settings for more information on how to change this setting.Against long exposure effects: Meridian “tracks” the exposure by means of the CNS O2 clock. At levels of 100% and higher there is risk of long exposure effects, and consequently Meridian will activate an alarm when this level of CNS O2 is reached. Meridian can also warn you when the CNS O2 level reaches 75% (see section CNS alarm). Note that the CNS O2 clock is independent of the value of ppO2max set by the user.

The CNS O2 clock increases when the oxygen partial pressure is higher than 0.5bar, and decreases when the oxygen partial pressure is lower than 0.5bar. Hence, while on the surface breathing air you will always be decreasing the CNS O2 clock. During the dive, the depth at which 0.5bar is reached for various mixes is as follows:

Air: 13 m / 43 ft

32% 6 m/20 ft

36%: 4m/13ft

FNOTE:• the O2 concentration of Gas d can

onlybesettoavaluehigherthantheO2concentrationforGas1.

•O2 concentration setting shown “- -“meansthatgasisdisabled.

•Meridian requires that the MODs ofGas1andGasdbeatleast3m/10ftapart.

•Setting the ppO2max value to OFFapplies to Gas 1 only. Gas d isalwayslimitedtoamaximumvalueofppO2maxof1.6bar.

•For oxygen concentrations of 80%and higher, the ppO2max is fixed at1.6barandcannotbechanged.

•TheMODforGasdistheswitchdepthfor that gas. This is what Meridianusesfor itscalculation,warningsandsuggestedswitchpoint.

•Whendivingwithmorethanonegasmixture,theNitroxresettimefunction(described in section 2.3.5) has thefollowingeffect:

•Gas1issetto21%•GasdissettoOFF.

3.10.1 Divingwithtwogasmixtures

Meridian is equipped with the ZH-L8 ADT MB PMG algorithm. PMG stands for Predictive Multi Gas, meaning that when you program more than one gas mixture, Meridian will predict the switch to the higher oxygen concentration gas at the depth that you specified and alert you at all times with a decompression schedule comprehensive of both gas mixtures that you programmed. In other words, you get full credit at any point during the dive for all the extra gas that you are carrying with you. At the same time Meridian can also show you what the decompression schedule would be if you were to finish the dive using only the gas mixture that you are currently breathing from, so that you can be prepared in the event that


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something did not work as planned.

Warning•Diving with two gas mixtures represents a

muchhigher risk thandivingwith a singlegasmixture,andmistakesbythedivermayleadtoseriousinjuryordeath.

•Duringdiveswithtwogasmixtures,alwaysmakesureyouarebreathingfromthetankthat you intend to breathe from. Breathingfromahighoxygenconcentrationmixatthewrongdepthcankillyou.

•Mark all your regulators and tanks sothat you cannot confuse them under anycircumstance.

•Beforeeachdiveandafterchangingatank,ensure that each gas mixture is set to thecorrectvalueforthecorrespondingtank.

•Get a proper training and certifications tomakemulti-gasdivespriorofmakingthem.

Meridian enables you to use up to two gas mixtures during the dive (air and Nitrox only). The two mixtures are labeled 1 and d, and must be in ascending order of the oxygen fraction.

1 dd

Time

Bottom mix

Diving with 2 gas mixtures

Deco mix

Dep

th

switching gas mixture during the dive

During the ascent phase, when you reach a depth corresponding to the MOD of gas d, Meridian will suggest that you perform the switch. An audible sequence goes off, and the text gas d starts flashing on the display together with the value of the MOD. You have 30 seconds to respond to this message, otherwise Meridian will consider that Gas d will not be used and adapts the decompression schedule accordingly. To confirm the gas switch, press seL/esC button.

FNOTE: Start breathing from the tankwith the new gas mixture beforeconfirmingaswitch.

WarningAlways make sure you are switching to theintended gas. Failure to do so may result inseriousinjuryordeath.

After you confirm the switch, the text gas d remains on the screen for five seconds without flashing.

switching back to a gas mixture with lower oxygen concentration

There may be situations in which you have to switch back to Gas 1 from Gas d. This can happen for instance if you want to descend again below the MOD for Gas d, or if for instance you have run out of Gas d during the decompression. At this point you can manually initiate the gas switch by pressing and holding SEL/ESC button. Meridian will display the text gas 1 and its MOD, flashing. At this point press seL/esC button to confirm the switch. Meridian will display the text gas 1 for five seconds without flashing and adapt the decompression schedule accordingly.

gas switch not carried out at the planned depth

If you fail to confirm the change to Gas d within the 30 seconds of when Meridian suggested it, Gas d is excluded from the decompression calculation and the decompression schedule is adapted

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accordingly, basically reflecting the fact that you will finish the dive using Gas 1 only.

FNOTE: if after Meridian has changedthedecompressionscheduletoreflectthemissedgasswitch, youdescendagain below the MOD for Gas d,Meridian reintroducesGasd into thecalculations and the decompressionschedulechangesaccordingly.

delayed gas switch

You can catch up on a planned gas mixture switch at any time by selecting the gas manually. press and hold SEL/ESC button to start the gas switch procedure. Meridian will show the text gas d and its MOD flashing on the display. This helps you verify that you are performing a switch to a safe gas. At this point press seL/esC button to confirm the switch. Meridian will display the text gas d without flashing and adapt the decompression schedule accordingly.

submerging below the Mod after a gas switch

If after having switched to Gas d you inadvertently drop again below the MOD for that mixture, the MOD alarm will immediately go off. Either switch back to Gas 1, or ascend above the MOD for Gas d.

3.11 Warningsandalarms

Meridian can alert you of potentially dangerous situations via warnings and alarms. you can only modify the warning and alarm settings via pC interface.

Warnings represent situations that require the diver’s attention, but ignoring them does not represent an immediate risk. It is up to you to decide which ones you would like to be active and which ones not. The available warnings are:

3.11.1 CNSO2=75%

Meridian tracks your oxygen uptake via the CNS O2 clock. If the calculated value of CNS O2 reaches 75%, Meridian will emit a sequence of audible beeps for 12 seconds

and the value of the CNS O2 will be flashing in the lower right corner. The flashing will continue until the value of CNS O2 drops under 75%.

CNS O2 = 75%

3.11.2 No-Stoptime=2minutes

If you wish to avoid unintentionally performing a decompression dive, Meridian can activate a warning

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