Monitor 2 Plus
Users Manual
CONTENTS
INTRODUCTION................................................2
WHAT IS A “DIVE COMPUTER”.......................2
DEFINITION OF COMPARTMENTS ............................................2
MULTI-LEVEL DIVING .................................................................2
DIVING RESPONSIBLY ...............................................................2
FEATURES OF THE M2+ ..................................2
THE COMPUTER SCREEN .........................................................2
THE ELECTRICAL CONTACTS................................................... 2
AUTOMATIC ACTIVATION ........................................................... 2
M2+ DISPLAY AND CONTACT LETTER DESIGNATIONS ........2
ACTIV A TING THE COMPUTER.........................3
CHECKING THE BA TTERY PO WER.................3
FUNCTIONS DURING THE DIVE ...................... 3
CURRENT DEPTH........................................................................3
DIVE TIME .....................................................................................3
MAXIMUM DEPTH........................................................................3
ASCENT RATE .............................................................................3
NO-STOP TIME ............................................................................. 4
DECOMPRESSION STOP INFORMATION ................................. 4
TOTAL ASCENT TIME ..................................................................4
SOS MODE ................................................................................... 4
FUNCTIONS AT THE SURFACE .......................4
WAIT MODE..................................................................................4
SURFACE MODE .......................................................................... 5
SURFACE MODE ICON................................................................5
WAIT -T O-FLY TIME.......................................................................5
DESA TURA TION TIME .................................................................5
SURFACE INTERVAL TIME ......................................................... 5
MICROBUBBLE WARNING .........................................................5
DIVING AT ALTITUDE .......................................5
ALTITUDE SECTORS...................................................................5
EXCEEDING THE AL TITUDE LIMIT ............................................6
SUMMARY OF ATTENTION MESSAGES AND
ALARMS.......................................................6
ATTENTION MESSAGES ............................................................ 6
ALARMS .......................................................................................6
OVERVIEW ...................................................................................7
DOWNLOADING THE MEMORY TO A PC ..................................7
MEMORY MODE................................................7
ACTIVATING MEMORY MODE....................................................7
SCROLLING THROUGH LOGGED DIVES..................................7
EXITING MEMORY MODE...........................................................7
PRE-DIVE PLAN MODE....................................8
OVERVIEW ...................................................................................8
ACTIVATION FROM READY-MODE ............................................8
ACTIVATION FROM SURFACE MODE .......................................8
PLANNING A DECOMPRESSION DIVE .....................................9
OVERVIEW ...................................................................................9
CARE BEFORE THE DIVE ...........................................................9
CARE DURING THE DIVE............................................................9
CARE AFTER THE DIVE ..............................................................9
ANNUAL DEALER INSPECTIONS & FACTORY SERVICE....... 9
CARE AND MAINTENANCE.............................9
HOW TO OBTAIN SERVICE .......................................................10
OPERATING TEMPERATURE ...................................................10
REPLACING THE BATTERY......................................................10
TECHNICAL SPECIFICATIONS......................10
OPERATIONAL PERFORMANCE ............................................. 10
NO-DECOMPRESSION MODEL ...............................................10
ZH-L8 ADT CALCULATION MODEL ..............10
TEMPERATURE ......................................................................... 10
ASCENT RATE AND MICROBUBBLE FORMATION ............... 10
SUMMARY....................................................... 1 0
INTRODUCTION
Congratulations on the purchase of your Monitor 2 Plus (M2+) dive
computer. Our designers have condensed important dive planning
information into a user-friendly dive instrument. By combining
graphics with bold alphanumerics, we have created an easy-to-use
computer that provides dive data at a glance.
As with all diving equipment, it is important to understand the
features and functions of the M2+. Before using the M2+, it is
essential to read this manual in its entirety. Contained within this
easy to read manual are illustrations to aid you in the complete
understanding of the computer.
Section 1 instructs you on diving with the M2+, including pre-dive
activation, descriptions of underwater displays, functions after the
dive, and diving at altitude. Section 2 shows you how to recall the
dive memory. Instructions on planning a future dive are given in
Section 3. Care & Maintenance tips are covered in Section 4. Lastly,
the reference section contains the technical specifications and a
description of the algorithm.
WHAT IS A “DIVE COMPUTER”
DEFINITION OF COMPARTMENTS
A dive computer is an instrument that mathematically simulates the
absorption and release of nitrogen by hypothetical tissue types in the
human body. These hypothetical tissues are commonly referred to as
“compartments.” Each compartment absorbs and releases nitrogen at
different rates. The M2+ tracks these compartments constantly,
providing you with up-to-the-minute decompression information.
MULTI-LEVEL DIVING
If you use, or have used, dive tables you know the total amount of
time you can stay under water is based on the maximum depth
reached during the dive. Dive tables, such as the U.S. Navy dive
tables, assume that you immediately descend to a single depth, stay
at that depth for the duration of the dive, then immediately surface
from that depth. This type of dive profile is referred to as a rectangular dive profile (figure 1). In reality, however, most recreational
divers go to the deepest depth first and make a gradual ascent to the
surface. This type of dive profile is referred to as a multilevel dive
profile (figure 2).
Multilevel diving is where the M2+ excels. By continuously calculating the nitrogen absorption/release of all the compartments, the
computer updates the amount of no-decompression time (NDT) you
have left. As you ascend to shallower depths, the computer credits
you with more allowable NDT; if you go deeper, it reduces the NDT
available.
FEATURES OF THE M2+
THE COMPUTER SCREEN
The M2+ has a large liquid crystal display (LCD) and features large
numbers and graphics. The screen is luminous for easy reading
during low light dives, including night dives and cave dives.
The illustration on the opposite page calls out each display number
or icon and provides a brief description for each one.
THE ELECTRICAL CONTACTS
All surface operations and mode changes are made by the use of four
electrical contacts placed around the M2+'s screen. These contacts
are identified as A, B, C and D (see figure below). As a rule, contact
A is always touched in conjunction with one of the other three
contacts. After entering different modes, such as Memory Mode or
Pre-Dive Planning Mode, contact B always decreases a value, and
contact C always increases a value (always in combination with A).
To make contact, simply moisten your fingertips and touch the
appropriate pair of contacts at the same time. Release the contact as
soon as the operation has been activated, usually no more than one
second.
AUTOMATIC ACTIVATION
The M2+ automatically activates and starts working as soon as it is
submerged in water. This means you can enter the water and start
diving without turning on the computer first.
Occasionally, when diving in fresh water, there is not enough
electrical conductivty in the water to complete the circuit between
contacts. If this is the case, the M2+ will activate using a secondary
pressure switch. Therefore, there may be slight delay between
entering the water and the computer going into Dive Mode.
M2+ DISPLAY AND CONTACT LETTER DESIGNATIONS
DIVING RESPONSIBLY
Figure 1
Rectangular Profile
Figure 2
Multi-Level Profile
ACTIV ATING THE COMPUTER
One of the nice features of the M2+ is that it automatically turns on
and starts working when you enter the water. However, its a good
idea to manually turn on the computer before a series of dives to
make sure it is working properly and to check the battery power. To
manually switch on the M2+, touch contacts A and D. Check the
display to make sure all the display elements are lit.
The M2+ is now in Ready Mode. The computer switches to Dive
Mode after entering the water and submerging below four feet. The
depth indication may be delayed for a few seconds.
Note: After three minutes of inactivity, the M2+ screen goes blank. This
indicates that the computer is in Sleep Mode. To "wake up" the
computer, touch contacts A & D.
DIVE TIME
Dive time, which is displayed in minutes, is the
amount of time spent below a depth of 4 feet. While
the dive time is running, the colon to the right of the
number flashes in one-second intervals. Maximum
dive time displayed is 199 minutes.
Note: If a dive lasts longer than 199 minutes, dive
time will roll over to 0 minutes.
Dive time display
MAXIMUM DEPTH
Maximum depth is the deepest depth reached
during the dive. It is only displayed when the
actual depth is more than three feet shallower
than the maximum depth.
Maximum depth
display
CHECKING THE BATTERY POWER
You can manually check the battery
power of the M2+. While in Ready
Mode or Surface Mode, touch
contacts A&D. The word "bat" will
be displayed along with the battery
power. Battery power is given as a
percentage, with 99% being the
highest percentage displayed. It is a
good idea to check the battery
power before you start a series of
dives.
FUNCTIONS DURING THE DIVE
CURRENT DEPTH
Current depth is displayed in one-foot increments down to a
maximum of 330 feet. When the depth is two feet or less, the depth
display is replaced with three dashes.
Note: Depth measurement is based on freshwater. When diving is salt
water, the depth displayed will be slightly greater than the actual depth,
depending on the salinity of the water.
ASCENT RATE
The optimal ascent rate varies between 23
and 67 ft/min. depending on the depth.
Ascent rate is displayed as a percentage of
the allowable ascent rate (rounded to the
nearest 10 %). For example, if the allowable
ascent rate at the current depth is 67 ft/min,
and you ascend at 33 ft/min, the ascent rate
will display 50%. If you ascend at 67 ft/min
the ascent rate will show 100%.
WARNING: The prescribed ascent
rate must be observed at all times!
Exceeding the prescribed ascent
rate can lead to microbubble
formation which can lead to
serious injury or death due to
decompression sickness.
If the ascent rate is 100% or more, the arrow appears. If the ascent
rate exceeds 140%, the arrow starts flashing. Also, an acoustic alarm
sounds when ascent rate is 110% or greater. The intensity of the
alarm increases as the percentage over the allowable rate increases.
Below is a summary of the ascent warnings.
Some Notes on ascent rate:
- The M2+ may require a decompression stop due to an improper
ascent rate, even if you stay within the no-stop limits.
- Decompression time necessary for the prevention of microbubbles
can increase greatly if the ascent rate is exceeded.
- At great depth, ascending too slowly may cause heightened satura-
tion of tissues and increase both decompression time and total
ascent time. At shallow depth, a slow ascent may shorten decom-
pression time because the tissues are desaturating during a shallow,
slow ascent.
- Excessive rates of longer periods are entered in the dive computer's
memory
Ascent Rate Display
Current depth display
at 100 feet
Current depth display at
2 feet or shallower
WARNING: Reduce your ascent speed whenever the
above alarms appear. Failure to do so may lead to serious
injury or death due to decompression sickness.
Rate
Optical
Alarm
Acoustic
Alarm
Ascent
NO-STOP TIME
No-Stop Time is the amount of time you can stay at the current
depth without making required decompression stops. This number is
displayed in minutes, with 99 being the highest number displayed.
If 99: is displayed, you have 99 minutes or more of no-stop remaining. No-stop time is easily identified by the no-stop arrow located
directly above it.
WARNING: It is unsafe diving practice to “push” the M2+,
or any other decompression tool, to its limits. Avoid nostop times of less than 3 minutes at any given depth.
WARNING: There is an acoustic alarm if no-stop time is
less than one minute. In this last minute, the no-stop
display shows a flashing 0. In order to prevent a decompression dive, you must ascend immediately.
WARNING: If you ascend shallower than the required
decompression stop depth, the DECO arrow will start
flashing and an acoustic alarm will sound. Due to the
formation of microbubbles, decompression obligation can
increase greatly if a decompression stop is ignored. When
the surface is reached during the decompression alarm,
the DECO arrow continues to flash to point out the risk of
a decompression accident. If you do not descend
immediately to the required stop depth, the Monitor 3 will
enter SOS Mode. Any decompression violation longer
TOTAL ASCENT TIME
Total Ascent Time is the addition of all the
decompression stop times plus the amount of
time it takes to ascend from the current depth
to the first decompression stop.
Note: Total ascent time is calculated with an
optimal ascent rate of 100% and normal work-
load. High workloads and different ascent rates
may change the total ascent time.
Total Ascent Time
Display
SOS MODE
If you ignore your decompression stop and
return to the surface (shallower than 4 feet)
for more than three minutes, the M2+
switches to SOS Mode. In SOS Mode, the
computer displays SOS instead of current
depth. While in SOS Mode, the computer
cannot be used for 24 hours. SOS Mode can
influence the computer's calculations for up
to three days after the incident due to the
presence of microbubbles.
No-Stop Time
Display
DECOMPRESSION STOP INFORMATION
If you exceed the no-stop limits, the
Monitor 3 will replace the no-stop time
with the deepest (first) decompression
stop depth (in feet) along with the
amount of decompression time (in
minutes) at that depth. When a decompression stop has been completed, the
next shallower decompression stop is
displayed, along with its required stop
time. When all decompression stops are
completed, the DECO arrow disappears
and the NO STOP arrow reappears.
No-stop time at 0
minutes remaining
Decompression Stop
Information:
Diver must make a 20-foot stop
for 3 minutes
FUNCTIONS AT THE SURFACE
WAIT MODE
After reaching the surface, the M2+
automatically switches into Wait Mode for
five minutes. This is the amount of time
necessary to recognize the end of the dive.
The five minute delay allows you to come to
the surface to orient yourself, then resume
the dive. If you stay at the surface longer
than 5 minutes, the dive is entered into the
logbook and the M2+ switches into surface
mode.
SOS Mode Display
Wait Mode Display
SURFACE MODE
Note: Surface Mode will stay visible for 3 minutes.
After that, the screen will go blank to save battery
power. To reactivate the Surface Mode display,
touch contacts A&D.
SURFACE MODE ICON
Five minutes after surfacing, the M2+ enters
Surface Mode. While in Surface Mode, the
Surface Mode Icon appears at the top of the
display.
Surface Mode Icon
WAIT-TO-FLY TIME
Wait-to-fly time is the minimum amount of
time you should wait before flying in a
commercial airliner. Wait-to-fly time is
displayed in hours and is denoted by the no-fly
icon immediately below it.
WARNING: Flying while the M2+ is
still displaying wait-to-fly time may
lead to serious injury or death from
decompression sickness.
Wait-to-fly Recommendations
The Divers Alert Network (DAN) has made
the following recommendations regarding
wait-to-fly time:
1. A minimum surface interval of 12 hours would be required in
order to be reasonably assured a diver will remain symptom free
upon ascent to altitude in a commercial jetliner (altitude up to
8000 ft/2400 m).
2. Divers who plan to make daily, multiple dives for several days,
or make dives that require decompression stops should take
special precautions and wait for an extended surface interval
beyond 12 hours before flight.
Both the Undersea and Hyperbaric Medical Society (UHMS) and
DAN agree that:
"There can never be a flying after diving rule that is guaranteed to
prevent decompression sickness completely. Rather, there can be a
guideline that represents the best estimate for a conservative surface
interval for the vast majority of divers. There will always be an
occasional diver whose physiological makeup or special diving
circumstances will result in the bends."
U.S. Divers recommends that you follow either the DAN recommendation, or the wait-to-fly time shown by the M2+, which ever is
longer.
DESATURATION TIME
Desaturation time is the amount of time it
takes to completely off-gas any residual
nitrogen in your system. Desaturation time is
displayed in hours and minutes.
SURFACE INTERVAL TIME
Surface interval time is shown immediately
after accessing Memory Mode. For more
information on accessing Memory Mode, see
page xx.
Wait-to-fly time
display
Desaturation time
MICROBUBBLE WARNING
Repetitive diving may cause microbubbles to
accumulate in the lungs if the surface
interval between dives is not long enough.
Ignoring decompression stops or an excessive
ascent rate can also lead to bubble formation.
In order to reduce the risk of decompression
sickness for future repetitive dives, the
surface interval should be planned long
enough to reduce the risk of decompression
sickness. If the M2+ calculates that the
formation of microbubbles may occur during
the surface interval, it will advise the diver
to extend the surface interval. The display
“Atn” (= attention) is visible in the depth
display area during the surface mode. While
“Atn” is displayed, the diver should not
undertake another dive.
Note: If a dive has to be made while Atn is
displayed, the amount of Atn-time for the
following dive can increase considerably.
During the dive, no-stop times will be much
shorter and decompression times will increase.
Microbubble
formation warning
Atn = Attention
DIVING AT ALTITUDE
The M2+ measures the atmospheric pressure
even while in Sleep Mode. If the computer
detects a higher altitude, it automatically
switches on and displays the adaptation time.
This is the time after which your body is
considered desaturated and stable at the
given altitude.
ALTITUDE SECTORS
Atmospheric pressure is influenced by altitude
and weather. The M2+ is interested only in the
actual atmospheric pressure value for use in
decompression calculations. However, it
indicates the altitude sector which corresponds
most closely with this pressure for normal
weather conditions. The altitude sectors and
their corresponding altitude is illustrated
below.
Even the smallest differences in the pressure sensors can cause two
computers at the same altitude to display different altitude sectors.
(Notice how the altitude sectors overlap in the illustration.) These
differences are not meaningful and do not interfere with the
operation of the computer. However, if there is an altitude indication
while at sea level, or two computers differ by 2 altitude sectors,
contact your U.S. Divers dealer for service.
Note: In order to assure optimal decompression even at higher altitudes,
the 10-foot decompression stop is divided into a 13-foot stop and 7-foot
stop. Therefore, the prescribed decompression stops, in order, are 7 ft,
13 ft, 20 ft, 30 ft ... 80 ft.
Altitude adaptation
time display
Adt=Adapt
switches
switches at
switches at
switches at
EXCEEDING THE ALTITUDE LIMIT
The M2+ operates normally up to an altitude
of 13,123 ft. If the altitude limit is exceeded,
the M2+ will display "HI" along with all the
altitude sectors.
If you make a dive after exceeding the
altitude limit the computer will not show any
decompression information; it becomes no
more than a depth gauge and bottom timer.
Also, Pre-Dive Planning Mode cannot be
started, since decompression information is
not available.
Diving display when
altitude limit has been
exceeded
SUMMARY OF ATTENTION MESSAGES AND ALARMS
The M2+ draws your attention to certain situations and warns you of
unsafe diving practices. Attention messages and alarms are always
visual and acoustical while underwater; they are only optical at the
surface except for the decompression alarm.
ALARMS
Alarms are communicated to you by symbols, letters, or
flashing icons. In addition, an acoustic warning sounds
during the duration of the alarm. An alarm occurs in the
following situations.
Fast ascent
Reduce your ascent rate
Missed decompression stop
Descend to the prescribed decompression
stop at once.
ATTENTION MESSAGES
Attention messages are given by symbols, letters, or flashing figures.
In addition, two short beeps can be heard, in intervals of 4 seconds,
in two different frequencies. Attention messages
appear in the following situations:
Altitude dive
During a change to a higher altitude, the M2+
displays an altitude sector icon and the corresponding adaptation time.
End of no-stop time
To avoid making a decompression dive, a "0"
flashes during the last minute of no-stop time
to alert you to ascend to a shallower depth.
Also, two beeps are sounded.
Microbubble warning (Atn)
This message is displayed when the M2+
calculates that there is an excess of microbubbles in your body tissues. Do not dive
while this message is displayed. If you dive
while the message is displayed, no-stop times
will be reduced and decompression times will
be longer.
Low computer battery
While diving, "bAt' alternates with the
maximum depth display. During Surface
Mode or Ready Mode, "bAt" flashes in the
maximum depth position. This indicates
battery charge is nearing 0%.
MEMORY MODE
OVERVIEW
The Monitor 2+ is able to display the details of the last 19 dives. Any
dive that lasts two minutes or longer is entered into memory. After
the memory is filled with all 19 dives, the oldest dive is deleted for
each new dive entered. All the dive information stays in memory
until the battery is removed.
The illustration on the opposite page shows all the information that
is logged for each dive.
DOWNLOADING THE MEMORY TO A PC
With the use of a separate interface kit, the Monitor 2+ has the
ability to download the details of the last 37 dives to an IBM
compatible computer. In addition, detailed information on the last
200 minutes of diving, sampled every 20 seconds, allows the software
to plot a graph depicting your actual dive profile and display the
computer information anywhere along the profile.
The interface kit and software available from your Authorized U.S.
Divers dealer.
Note: The procedures for downloading data to a personal computer are
described in the manual that comes with the interface kit.
ACTIVATING MEMORY MODE
From Ready Mode or Surface Mode,
touch contacts A & C. The computer
will emit one beep and the Memory
Mode icon will appear at the top of
the screen. If activating from Surface
Mode, the current surface interval
also appears.
Activating Memory Mode from
Surface Mode
Touch Contacts A & D to confirm the selection. After a few moments,
the information for the most recent logged dive appears.
Note: If you are only checking surface time, you can immediately return
to Surface or Ready Mode by touching contacts A & B instead of
touching A & D.
Confirm the selection by
touching contacts A & D
SCROLLING THROUGH LOGGED DIVES
To scroll back through the last 19 dives in memory (towards the
oldest dive), touch contacts A & C. To scroll forward through the
memory (towards the most recent dive), touch contacts A & B.
Scroll back through memory
by touching contacs A & C
Typical Memory Mode
display
Scroll forward through
memory by touching contacts
A & B
EXITING MEMORY MODE
To exit Memory Mode, touch contacts A&D. If there is no activity for
three minutes while in Memory Mode, the computer will automatically switch back to Surface or Ready Mode.
PRE-DIVE PLAN MODE
OVERVIEW
The Monitor 2+ has a built-in dive planner that allows you to plan
both no-stop dives and decompression dives. The planner takes into
account the temperature of the most recent dive and altitude.
WARNING: Planned decompression dives violate the
responsible diving practice standards of every major
diving organization. Recreational or sport scuba divers
should not attempt decompression dives. Only professional divers with extensive experience, training, and the
appropriate equipment for decompression diving (including the presence of an on-board recompression chamber)
should attempt to plan a decompression dive. Those who
attempt decompression dives must be willing to accept an
increased risk of decompression sickness.
You can access the Pre-Dive Plan Mode form either Ready Mode or
Surface Mode. When you access the planner from Surface Mode, you
have the option of adding surface-interval time to plan for a dive at
some point later in the day.
ACTIVATION FROM READY-MODE
STEP 1
From Ready Mode, touch contacts A & B. The computer
will emit one beep and the Dive Plan Icon will appear at
the top of the screen.
ACTIVATION FROM SURFACE MODE
STEP 1
STEP 2
From Surface Mode, touch contacts A & B. The computer
will emit one beep and the Dive Plan Icon will appear at
the top of the screen.
Surface Mode
Touch contacts A & D to
confirm the selection. The
words "Add" and "Int" appear
along with a flashing surface
interval time.
Ready Mode
NOTE: Always moisten your fingertips before touching the contacts.
Otherwise, you cannot get a good electrical connection. Contacts only
need to be touched momentarily unless noted otherwise.
STEP 2
STEP 3
Touch contacts A & D to
confirm the selection. The word
RUN will flash for about five
seconds and then start scrolling
through the available timedepth combinations.
The Monitor scrolls from 50 to
200 feet in 10-foot increments.
For each depth the computer
gives the maximum allowable
no-stop time at that depth.
STEP 3
Note: Surface interval time increases in 15 minute increments for the
first 6 hours, 30 minute increments from 6 to 12 hours, and 1-hour
increments after that.
STEP 4
If you do not want to add any additional surface time, go
to step 4. If you do want to add surface time, touch
contacts A & C. If you add too much surface time and
want to decrease it, touch contacts A & B.
Increase Time
After adding the desired amount of surface interval time,
touch contacts A & D. The word "run" flashes for a few
moments, then the Monitor starts scrolling from 50 to
200 feet in 10-foot increments. For each depth the
computer gives the maximum allowable no-stop time at
that depth.
Decrease Time
Note: If you want to stay longer than the
no-stop time limit, proceed to "Planning a
Decompression Dive" on page 36.
PLANNING A DECOMPRESSION DIVE
Before planning a decompression dive, reread the import warning at
the beginning of this section.
STEP 1
When the Monitor 2+ scrolls to
the desired depth, touch
contacts A & D. The word “Add”
appears in the depth zone, the
flashing dive time is now one
minute more than the allowable
no-stop time, and all decompression information is
displayed, including stop depth,
stop time, and total ascent time.
CARE AND MAINTENANCE
OVERVIEW
The M2+ is a robust instrument designed to withstand the rigors of
SCUBA diving. However, you still need to protect it from shock,
extreme heat, chemical attack, and tampering.
Even though the M2+’s material is tough and durable, it is susceptible to chemical attack and scratches. Chemical attack can be in the
form of spray propellants, gasoline fumes in your garage or boat, and
alcohol. U.S. Divers cannot replace scratched gauge faces. However,
small scratches naturally disappear underwater.
CAUTION: Never use aerosol sprays, including silicone
sprays, on or near the M2+. The propellants may chemically attack the plastic, causing the plastic case to crack.
STEP 2
STEP 3
Note: If there is no activity during the Pre-Dive Planning Mode for three
minutes, the M2+ automatically returns to Surface Mode or Ready
Mode.
STEP 4
Increase the dive time by touching contacts
A & C. If you increase the dive time too much and want
to reduce it, touch contacts A & B.
Increase Time
When you reach the desired dive
time, release the contacts. After a few
moments, the Monitor 2+ will display
the new decompression information,
including the first decompression
stop, time at the first stop, and total
ascent time. You can then, as shown
in step 2, increase and decrease the
dive time as you wish.
To return to the pre-dive scrolling,
touch contacts A & D. If you want to
To return to Surface Mode or Ready Mode, touch
contacts A & D until you hear two beeps.
WARNING: If two or more divers using computers are
planning a dive, planning for all divers must be based on
the dive computer showing the shortest no-stop times.
Failure to do this may lead to serious injury or death from
Decrease Time
CARE BEFORE THE DIVE
The M2+’s plastic housing is made of a shock resistant resin. This
housing protects the M2+ from the normal bumps that occur when
diving. However, the computer cannot withstand the impact of heavy
objects, such as weight belts or SCUBA cylinders. Impact from heavy
objects is the most common cause of computer damage. When you set
up your dive gear on a boat or the beach, keep the M2+ protected
until you are ready to dive. Never leave the computer exposed where
someone could accidentally step on it, or drop something on it.
CARE DURING THE DIVE
The most common damage inflicted on a computer while underwater
is scratches to the computer face. Scratches occur when a dangling
computer console gets dragged over coral or rocks. Most buoyancy
compensators have gauge hose retainers that keep the computer
close to your body for easy access and reduce the possibility of
scratching the computer face.
CAUTION: Scratches to the computer body or gauge face
are not covered by the Two-Year Limited Warranty
CARE AFTER THE DIVE
CAUTION: If the M2+ is not attached to a first-stage
regulator while soaking (explained below), make sure that
water is not allowed to enter the high pressure hose.
Water entering the submersible pressure gauge (SPG) via
the high pressure hose may cause damage to the internal
components.
After each day of diving, soak the M2+ in a warm, fresh water bath
to dissolve salt crystals. To dissolve heavy salt buildup, use a slightly
acidic vinegar/water bath. After removing the computer from the
bath, rinse thoroughly with fresh water. Towel dry the computer
before final storage. Place the M2+ in a cool, dry and protective case
to transport.
If the M2+ is in a console, it should be rinsed at the same time the
regulator is rinsed. Connect the first-stage to a charged SCUBA
cylinder. Turn on the cylinder valve and submerge the whole
regulator/tank system in a bath of water. By applying pressure to
the regulator, you absolutely prevent any water from entering the
regulator, including the high pressure hose.
ANNUAL DEALER INSPECTIONS & FACTORY SERVICE
The M2+ should be inspected annually by an Authorized U.S. Divers
Dealer. The dealer will perform a depth accuracy test, function
check, and routine inspection for damage or wear. To keep the twoyear limited warranty in effect, this annual inspection must be done
one year from the purchase date, plus or minus 30 days. U.S. Divers
recommends that you continue to have yearly inspections to ensure
the M2+ is working properly, even after the warranty period expires.
An annual inspection record is provided in the rear of this manual,
which should be signed by the technician after each inspection. The
cost of this service is not covered under the two-year limited
warranty. Also, be sure to record any factory services that are
performed.
If you ever doubt the accuracy of the M2+’s depth readings, DO NOT
dive with it until you have it inspected by an Aqua Lung dealer.
Some dive stores who provide this service do not have test gauges on
their pressure chambers as accurate as the depth sensor on the M2+.
Therefore, if you request a depth check, verify that the test chamber
gauge accuracy is better than ±2 feet.
If the facility does not have the special tools to follow these service
procedures, have the dealer return the M2+ directly to Aqua Lung.
HOW TO OBTAIN SERVICE
Factory service for the M2+ was discontinued in 1997. If a battery
change is needed, please contact one of the following Aqua Lung
dealers:
1.Sea Sports, Houston, TX
281-894-4488
e-mail: ssscuba@flash.net
2.Underseas Scuba Center, Villa Park, IL (Chicago area)
630-833-8383
e-mail: bruce@underseas.com
OPERATING TEMPERATURE
The M2+ operates normally between 12oF to 122oF (-10oC to 50oC).
You may notice the liquid crystal display (LCD) becoming sluggish at
extremely low temperatures. This is normal and will not affect the
computer’s accuracy.
It is possible to damage the electronics if left exposed to direct
sunlight or in a hot, confined space (like a car trunk). After the dive,
cover the computer and keep it out of the sun. If inadvertently left in
direct view of the sun, the LCD may become totally black. If this
occurs, immediately immerse the M2+ in cool water. The display
should recover its normal appearance after a few minutes. Damage
from extreme heat or cold is not covered under the two-year limited
warranty.
REPLACING THE BATTERY
The M2+'s battery is not user-replaceable. It must be returned to the
dealer or factory for replacement. If you notice any low battery
warnings, have the battery changed as soon as possible. Refer to the
previous section "How to Obtain Service" for information on returning the M2+ to U.S. Divers Co.
TECHNICAL SPECIFICATIONS
OPERATIONAL PERFORMANCE
Depth Range: ....................... 0-330 feet
Time Measurement: ............ 0-199 min.; Quartz timing
Temperature Range: ........... 14oF to 122oF (-10oC to 50oC)
Display: ................................. High contrast, custom liquid crystal with
back luminescence
HP Hose Connection: .......... 7/16" UNF regulator HP port
Dive Log Mode ..................... Stores last 37 dives in memory
After 37 dives, adds latest dive to
memory, deletes oldest dive (37 most
recent dives are retained in memory)
Altitude Range: .................... 0-13,200 feet above sea level;
Full computer functions up to 13,200 ft.
Battery: ................................. LR07 long life lithium battery (factory
replaceable only)
Module Weight..................... 150 g (5.29 oz)
Module Dimensions ............. 3.875" tall x 2.28" wide x .9" deep
NO-DECOMPRESSION MODEL
• ZH-L8 ADT
• 8 tissue compartments, 5 to 640 minutes
• Decompression stop depths at 10 to 80 feet in 10-foot increments
ZH-L8 ADT CALCULATION MODEL
The M2+ uses a new calculation model known as the ZH-L8 ADT.
This model uses eight compartments or "tissue" groups with halftimes ranging from 5 to 640 minutes. This calculation model is based
on the most current research conducted by the late Dr. A.A.
Buhlmann. Most computer decompression models only take into
account time and depth; the M2+ model also factors in other
physiological factors, including temperature and ascent rate.
TEMPERATURE
Blood perfusion to the body's organs is not constant. Skin and muscle
tissues are especially subject to changes in blood perfusion, depending on temperature. Changes in blood perfusion to these organs
change their nitrogen saturation tolerance. The ZH-L8 ADT model
takes these effects into account and thus the "skin" and "muscle"
compartments in the M2+ have variable half-time periods and
saturation tolerances.
Decompression information is calculated according to the diver's
individual decrease in skin temperature. The decrease in skin
temperature is based upon the water temperature and the dive time.
By considering these changes in saturation, the time that must be
spent at the surface prior to flying can be considerably lengthened,
depending on the depth, time, and temperature of a dive.
ASCENT RATE AND MICROBUBBLE FORMATION
The ZH-L8 ADT model considers nitrogen in both its dissolved and
gaseous phase (microbubbles). Formation of microbubbles is
considered to be a strong indicator of a high risk of decompression
sickness. The model calculates the formation of microbubbles
depending on various assumed influences in arterial and venous
blood. During normal, slow ascents, microbubbles form mainly in
venous blood. During fast ascents, microbubbles may also form in
arterial blood and the body's tissues. If a particular dive profile
results in the formation of microbubbles, decreased bottom time and/
or increased decompression times, and increased wait-to-fly times,
will be indicated.
Microbubbles can form if the diver makes a fast ascent, ignores
decompression stops, or makes repeated ascents during a dive (yo-yo
diving). These microbubbles can form in arterial blood and body
tissues. If these microbubbles partially impair circulation, the rate of
gas diffusion and saturation tolerance of surrounding tissues are
changed. If required, both decompression time and remaining bottom
time will be adjusted in such a way that already existing
microbubbles will stop growing. Increased decompression time will
also assist those local areas of impaired circulation to desaturate
with less risk of decompression sickness.
The calculation of microbubbles results in altered ascent instructions. If microbubbles are assumed to be present based on the data
used by the M2+, the ascent rate is reduced to 23 feet/minute. This
will help prevent the formation of microbubbles in the arterial
circulation and minimizes formation of microbubbles in the venous
circulation after the dive.
SUMMARY
With its new decompression model, the M2+ is a versatile tool which
can increase your diving comfort and safety. As with any diving tool,
however, ultimate responsibility for diving safety remains with the
individual diver. The same responsible diving practices taught by all
diving certifications are still absolutely necessary in order to safely
dive with the M2+.
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