Cochran Nemesis IIa NITROX User manual

1
Limited Warranty
To the original owner only, Cochran Undersea Technology, a division of Cochran Consulting, Inc.,
guarantees this dive computer to be free of defects in both materials and craftsmanship under
normal SCUBA use for 24 months from the date of shipment to your Authorized Dealer. Failing to
provide proper care will cause this warranty to be null and void. Any defect not excluded in the
limitations section below will be repaired, replaced, or replaced with a refurbished unit, at
Cochran Undersea Technology’s discretion, free of charge. Purchaser is responsible for ship-
ping the product to the Cochran Undersea Technology Service Department and for all associated
freight and insurance costs. This warranty IS NOT transferable. All correspondence concerning
this warranty MUST be accompanied by a photocopy of the original sales receipt. The shipment
date is recorded on the outside of the product box.
Your warranty registration card must be returned to Cochran Undersea Technology within 15
days of the purchase date. Failing to do so will cause this warranty to be null and void. Charges
for the Annual Maintenance are not covered under this warranty. The Annual Maintenance
includes accuracy verification of the depth and pressure sensors, overall calibration and overall
performance. You should return your dive computer to the place of purchase for this service to
be performed.
WARRANTY LIMITATIONSANDEXCLUSIONS
This warranty DOES NOT cover any damages including, but not limited to, those resulting from
abuse, tampering, battery leakage, accident, or lack of proper care. Proper care includes having
anAnnualMaintenanceperformed. Additionally, any modifications or repairs to this unit performed
by anyone other than an authorized Cochran Undersea Technology dealer will void this warranty.
All plastics, o-rings, batteries, or damage due to accident, abuse, modification, or tampering are
NOT covered.
STATEMENT OF LIMITED LIABILITY
A mathematical model is used by this dive computer to calculate nitrogen absorption into the body
as well as nitrogen elimination during a surface interval between dives. While great care and
extensive research has gone into the making of this model, variables such as, but not limited to,
dehydration, being overweight, age and old injuries may require a more conservative use of this
instrument. COCHRAN UNDERSEA TECHNOLOGY DOES NOT GUARANTEE THE PREVEN-
TIONOFDECOMPRESSION SICKNESSOR ANY OTHERINJURYTHATMAY REQUIRE TREAT-
MENTIN A RECOMPRESSION CHAMBER. This divecomputer should be used solelyas a guide,
providing the trained and certified diver the information needed to make safe diving decisions. It is
expressly understood that by buying and/or using this dive computer, the diver assumes ALL risk
as to its quality, performance, and accuracy. Cochran Undersea Technology, its distributors, or
retailers will not be held liable for any personal injuries or other damages resulting from its opera-
tion, even if Cochran Undersea Technology has been advised of such occurrences and damages.
Cochran Undersea Technology supports and strongly agrees with maximum depth limits of 130
feet for recreational SCUBA diving, as set by recognized certification agencies. Cochran Undersea
Technology in no way encourages diving deeper than this limit. You should always adhere to safe
diving practices which include, but are not limited to, always using the buddy system, diving within
your own limitations, having your tanks filled only by a certified NITROX blending station, and
making only dives that do not require decompression.
(C) 1996 Cochran Undersea Technology
Nemesis IIa Nitrox Manual

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FCC Label
FCC ID: LYP744556-01
This device complies with Part 15 of the FCC Rules. Operation is subject to the
following two conditions: (1) this device may not cause harmful interference, and (2)
this device must accept any interference received, including interference that may
cause undesired operation.
Interference Statement
NOTE: This equipment has been tested and found to comply with both the limits for a
Class B digital device and an intentional radiator, pursuant to Part 15, Subpart B/C of
the FCC Rules. This equipment generates, uses, and radiates radio frequency energy.
Ifnot installedand used inaccordance withthe instructions, itmay causeinterferenceto
radio communications.
The limits are designed to provide reasonable protection against such interference in a
residential situation. However, there is no guarantee that interference will not occur in a
particular installation. If this equipment does cause interference to radio or television
reception, which can be determined by turning the equipment on and off, the user is
encouraged to try to correct the interference by one or more of the following measures:
·Reorient or relocate the receiving antenna of the affected radio or television.
·Increase the separation between the equipment and the affected receiver.
·Connect the equipment and the affected receiver to power outlets on separate
circuits.
·Consult the dealer or an experienced radio/TV technician for help.
MODIFICATIONS
Changes or modifications not expressly approved by Cochran Consulting, Inc. could
void the user’s authority to operate the equipment.
SHIELDED CABLES
This product is designed to be used only with the Analyst interface cable (RS-232) to
maintain compliance with FCC Regulations.

3
Patent Information
Protected under one or more of the following patents:
US 4949072, 4999606
AUS 591804
EUR 0305450
Other patents pending. All specifications subject to change without prior notice. Nem-
esis is a trademark of Cochran Consulting, Inc. Copyright 1996 Cochran Consulting,
Inc.

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TABLE OF CONTENTS
Limited Two-Year Warranty ................................................... 1
FCC Label ................................................................................ 2
Patent Information................................................................... 3
Table of Contents .................................................................... 4
Introduction ............................................................................. 8
SECTION I. The NEMESIS™ IIa NITROX: OVERVIEW ........ 9
Nitrox-specific Functions
AltitudeAdaptation.................................................................... 9
Intelligent Deep Dive Compensation................................ 9
Salt Water/Fresh Water Compensation ............................ 9
Three-Blend Capability..................................................... 10
Equivalant Air Depth......................................................... 11
CNS and OTU Oxygen Toxicity........................................ 11
Installation.............................................................................. 13
Activation ............................................................................... 13
Operating Modes
Self-Diagnostic Mode ....................................................... 15
Surface Mode .................................................................... 16
Predive Prediction Mode .................................................. 18
CNS/OTU Toxicity Percentage Display ........................... 19
O2 Mix Display................................................................... 20
Battery/Altitude Display.................................................... 21
Logbook Mode .................................................................. 22
Subsurface Mode.............................................................. 24
Emergency Decompression Mode .................................. 26
Gauge Mode ...................................................................... 29
SECTION III. EXPLANATIONS.............................................. 31
Description of Functions ..................................................... 32
Altitude Diving................................................................... 32
Ascent Rate ....................................................................... 33
AscentRateBar Graph............................................................36
BATT .................................................................................. 33
BOTTOM ............................................................................ 33
BP....................................................................................... 34
CEILing .............................................................................. 34

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DEPTH ................................................................................ 35
DIVE ................................................................................... 35
MAX DEPTH ...................................................................... 35
Metric ................................................................................. 36
MissionOTUDose....................................................................36
REMAINing TIME AIR ........................................................ 36
REMAINing TIME NDC...................................................... 36
REMAINing TIME DEC ...................................................... 37
SURFace Time .................................................................. 37
TANK.................................................................................. 37
TEMP.................................................................................. 37
Time-To-FLY ...................................................................... 38
AUDIBLE & VISUAL WARNINGS.......................................... 39
User Defined Maximum Depth ......................................... 39
1/2 Tank Pressure Alarm................................................... 39
Low On Air ......................................................................... 39
Ceiling Violation ................................................................ 40
Breathing Parameter Alarm.............................................. 40
Ascent Rate Alarm ............................................................ 40
Low Battery Voltage ......................................................... 40
Gauge Mode Alarm ........................................................... 41
Two-Minute Warning ......................................................... 41
60 Foot Decompression Stop Warning ........................... 41
Entering Emergency Decompression Mode................... 41
Oxygen Tolerance Units (OTU) Warning:......................... 41
Central Nervous System (CNS) Oxygen Toxicity.............41
MaximumPPO2 Alarm............................................................42
QUESTIONSANDANSWERS......................................................43
SECTION IV. CARE AND MAINTENANCE........................... 45
Normal Care and Maintenance ........................................ 47
Rinsing and Cleaning ....................................................... 47
High-pressure Transducer Care ...................................... 47
Battery Type and Replacement........................................ 47
Battery Care ...................................................................... 48
Annual Maintenance ......................................................... 49

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SECTION V. TECHNICAL SPECIFICATIONS ...................... 51
Replacement Parts ........................................................ 53
SECTION VI. ACCESSORIES............................................... 55
Field Programmer.................................................................. 56
Limited 90-Day Warranty .................................................. 56
Overview............................................................................ 67
Installation ......................................................................... 67
Analyst ................................................................................... 61
Features of the Analyst Software Package..................... 61
Minimum Hardware Configuration .................................. 61
Iinstallation of the DCI Software to the PC ..................... 62
Quick Start ......................................................................... 62
Detailed Software Installation .......................................... 62
Installation of the Data Probe to the PC .......................... 63
Attaching Data Probe to the Dive Computer................... 64
Keyboard Keys and their Usage...................................... 65
Uploading Dive Data......................................................... 66
Files.................................................................................... 66
Statistics ............................................................................ 67
Profiles............................................................................... 68
Logbook ............................................................................ 70
Configuration .................................................................... 70
Printing........................................................................................71
DAN Research File...................................................................71

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Introduction
Your NEMESIS™ IIa NITROX Dive Computer from Cochran Undersea Technology is
one of the most advanced instruments made for this application. It incorporates more
user-programmable functions than any other dive computer made, yet is one of the
simplest to use. Once your personal preferences and perhaps some dive site or
condition-specific settings are entered, its computing power goes to work in the back-
ground. What you, the diver, see is all the critical information you need, in an informa-
tive and easy to comprehend display, with minimal distraction.
With this manual, the basic operating information is presented first, followed by more
technical and detailed sections for reference. Following are the sections you will find
as you get acquainted with your NEMESIS™ IIa NITROX. We hope you find this format
helpful, informative, and readily absorbed.
I. OVERVIEW. This section provides a brief look at several of the key functions
and features of the NEMESIS™ IIa NITROX.
II. INSTALLATION AND ACTIVATION. This section details the steps to ensure
proper installation of your NEMESIS™ IIa NITROX to your regulator as well as
providing information on how to activate your unit.
III. OPERATING MODES. This section illustrates a typical display in each of the
various operating modes of your dive computer, explains what is being shown,
then makes reference to appropriate items in SECTION IV for more detailed
explanations.
IV. EXPLANATIONS. This section goes into much more detail on each function,
how it relates to other information, and, where appropriate, what choices are
available with regard to user programmable functions.
WARNINGS. A number of audible and visual warnings are generated by your
NEMESIS™ IIa NITROX when circumstances warrant. Many of these may be
set by the user; this section explains their meanings and user choices.
QUESTIONS AND ANSWERS. We answer the most frequently asked ques-
tions about the NEMESIS™ IIa NITROX and its operation.
V. CARE AND MAINTENANCE. This section details the basic maintenance and
care necessary to assure optimum useful life from this device.
VI. TECHNICAL SPECIFICATIONS. This section lists the technical specifica-
tions for your NEMESIS™ IIa NITROX.
VII. ACCESSORIES. This section contains the operational manual for the Field
Programmer as well as the Analyst Personal Computer Dive Computer Inter-
face program.

9
The NEMESIS™ IIa NITROX: Overview
In addition to its standard time/depth-based decompression algorithm, the NEM-
ESIS™ IIa NITROX has incorporated the influence of additional physiological factors
such as Altitude, Temperature, Ascent Rate, and Workload. However, the NEMESIS™
IIa NITROX allows the diver, via the optional Analyst PC Interface, to disable the Tem-
perature and/or Workload decompression compensation should the diver deem a
particular diving situation would so warrant. Calculation of Central Nervous System
Oxygen Toxicity (CNS), Mission Oxygen Tolerance Units (OTU's), and the Partial Pres-
sure of Oxygen (PPO2) is yet another added feature of this algorithm. Twelve half-time
compartments ranging from 5 minute to 480 minute theoretical tissue groups are
used. An added degree of conservatism from 0 to 50% may also be added to the base
algorithm if the diver should so desire. You will find that this unit is extremely user
friendly and can be customized to your individual diving conditions and practices.
Some additional factors that influence the decompression algorithm of your NEM-
ESIS™ IIa NITROX are detailed below.
Altitude Adaptation
The NEMESIS™ IIa NITROX continues to monitor changes in barometric pressure
that may occur during travel to and/or from diving destinations. Should a significant
change in altitude occur due to travel to a higher elevation dive site, your unit will
display the time, in hours, that you should wait before diving in order to "off-gas" all
residual nitrogen present as a result of this altitude change. This "adaptation" time is
displayed as Time-To-Fly. Should you wish to begin diving prior to completing the
adaptation time, the NEMESIS™ IIa NITROX will treat your first dive of the day as a
repetitive dive with appropriate reductions in no-decompression (NDC) limits.
Intelligent Deep-Dive Compensation
Modern research has suggested that failing to make each repetitive dive profile, in a
diving day to a shallower depth (inverted profiles) and/or diving square or "sawtooth"
profiles greatly increases your susceptibility to decompression sickness. Your NEM-
ESIS™ IIa NITROX is constantly monitoring the residual nitrogen in all twelve half-time
compartments and modifies its algorithm to alert you to this danger. The intelligent
deep-dive compensation provides real-time adjustment of this factor based upon
residual nitrogen. It is strongly recommended that you always make your first dive of
a diving day the deepest dive, with each repetitive dive to a shallower depth than that of
the previous dive.
Sea Water/Fresh Water Recognition
As you no doubt learned in your entry-level SCUBA class, there is a difference of
approximately three percent between feet of fresh water and feet of sea water. Your
NEMESIS™ IIa NITROX automatically "senses" the type of water you are in upon
entering the Subsurface Mode and provides depth readings in either feet of fresh
water or feet of sea water. With this unique feature, you are assured of extremely
accurate depth information for the medium of water in which you are diving.

10
Enriched Air Nitrox, Three-Blend Capability
Your NEMESIS™ IIa NITROX has the unique ability to provide the diver with the ability
to select a single bottom mix and TWO decompression mixes. Using the included
Field Programmer, you can set the oxygen percentage for the three different mixes
within the following ranges:
Mix1: 21.0% to 50.0% in 0.1% increments
Mix2: 21.0% to 99.9% in 0.1% increments
Mix3: 21.0% to 99.9% in 0.1% increments
In order to obtain the full benefit of this unique feature, you must designate Mix 1 as
your bottom mix, Mix 2 as your first (deeper) decompression mix and Mix 3 as your final
(shallower) decompression mix. The TU must be attached to the cylinder contain-
ing Mix 1. Here is how the automatic switching occurs:
1. With the TU attached to Mix 1, it continually "senses" a drop in cylinder pressure until
you are prepared to switch to your first decompression mix (Mix 2).
2. Once you have made the switch to Mix 2, the TU no longer senses a drop of cylinder
pressure from your Mix 1 cylinder and automatically changes its algorithm to Mix 2.
3. For Mix 3, you will be required to not only have programmed the oxygen percentage
for this mix, but also the:
a) bottom time you will be beyond at which you will begin breathing from Mix 3
b) the maximum depth at which you will begin breathing from Mix 3
when switching to this final decompression gas. The time and depth do not have to be
exact. They are simply used as a benchmark with the necessity of both being met in
order to allow the algorithm switching to Mix 3. We find that most divers participating
in this type of extreme diving usually have a bottom time of greater than 20 minutes
before beginning to decompress on a second decompression gas. Therefore, they
leave the bottom time factor set for 20 minutes. The depths at which a switch to Mix 3
is allowed in the algorithm is limited to a maximum of 30 feet.
NOTE: As you will discover in the Subsurface Mode section of this manual, your
NEMESIS™ IIa NITROX displays your breathing rate (BP) on the alternate display of
the WU. If the BP is displaying 0, Mix 2 is being calculated in the algorithm. Mix 3 is
indicatedby displaying a BP of 99. Should you switch backto your bottom mix(Mix
1), your TU will sense a drop in cylinder pressure and the Mix 1 algorithm will be
calculated. This switching between Mix 1, 2, and 3 is continuous based upon the
BP and current depth. Mix 1 BP is displayed between 1 and 98.
The following describes the various factors that determine which mix is being calcu-
lated in the algorithm:
Mix 1: TU senses drop in cylinder pressure with BP between 1 and 98 displayed.
Mix 2: TU does not sense a drop in cylinder pressure, BP displays 0; bottom time and
depth factors for Mix 3 are not met.
Mix 3: TU does not sense a drop in cylinder pressure, BP displays 99, bottom time and
depth factors for Mix 3 are met.
NOTE: For Mix 3, even though no drop in cylinder pressure is detected, BP will
display 99 as a means of informing the diver that the Mix 3 algorithm is being

11
calculated. The ability to switch mixes MUST be enabled via the Analyst. If you do
not have this program, your Authorized Dealer can perform this operation.
In addition, Mix 1 is always calculated for the first ten minutes of each dive regardless
of the BP. This allows you to "swim" your stage bottles down your ascent line at the
beginning of the dive. You can also vary the responsiveness of the Breathing Param-
eter calculations via the ANALYST. All three mixes are enabled at the factory and set to
21.0% oxygen.
Equivalent Air Depth
Your NEMESIS™ IIa NITROX uses Equivalent Air Depth (EAD) in determining the no-
decompression limits for each individual dive. A standard NOAA equation is used to
determine the EAD based upon the oxygen percentage entered. This equation is:
(1 - O2%) ´´
´´
´(D + 33)
EAD = ¾¾¾¾¾¾¾¾¾¾¾¾¾¾¾¾
¾¾¾¾¾¾¾¾¾¾¾¾¾¾¾¾
¾¾¾¾¾¾¾¾- 33
.79
Where O2is entered in decimal form and Dis the actual depth in feet.
For example, if you were diving with NOAA II (36% oxygen) to 70 feet, the EAD used for
determining your no-decompression limit would be:
(1-.36) ´´
´´
´(70+33)
EAD = ¾¾¾¾¾¾¾¾¾¾¾¾¾¾¾¾
¾¾¾¾¾¾¾¾¾¾¾¾¾¾¾¾
¾¾¾¾¾¾¾¾- 33
.79
.64 ´´
´´
´103
¾¾¾¾¾¾¾¾
¾¾¾¾¾¾¾¾
¾¾¾¾- 33 = 50.44 feet
.79
Therefore, the no-decompression time for this example would be calculated to an
EAD of 50.44 feet.
Central Nervous System (CNS) Oxygen Toxicity
An additional consideration for the NITROX diver is Oxygen Toxicity. Your NEMESIS™
IIa NITROX will provide audible and visual warnings to alert you to this hazardous
condition.
Maximum exposure time for a given depth is calculated based on the Partial Pressure
of oxygen (PPO2). The following standard formula is used to determine the PPO2:
D X O2% = PO2level
Where O2is entered in decimal form and Dis the actual depth in atmospheres
absolute.

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For example, if you were diving to 86 feet with NOAA II your PPO2 level would be:
3.6 ( or 86 ¸¸
¸¸
¸33 + 1) X .36 = 1.296
which would be rounded up to PPO2 = 1.3. PPO2 levels from 0.5 to 1.6 are calculated.
Exceeding a PPO2 of 1.6 will greatly increase the probability of the immediate onset of
CNS Oxygen Toxicity. While various training organizations have established maxi-
mum PPO2limits, the maximum exposure times and their associated PO2levels used
in this dive computer's calculations are shown on the following table:
PPO2LEVEL Max Bottom Time (minutes)
.5 1304
.6 719
.7 496
.8 379
.9 306
1.0 257
1.1 221
1.2 194
1.3 172
1.4 149
1.5 110
1.6 44
Your dive computer calculates CNS or OTU toxicity percentages and it issues a unique,
five double-beep audible alarm once per minute should you reach 75 percent of the
associated maximum limit. In addition to this audible warning, the WARNING legend
will appear and flash AND the TEMPerature digits will be replaced with the current
calculated CNS Oxygen Toxicity percentage. This warning will continue until the calcu-
lated toxicity percentage is less than 75 percent. For example, the maximum bottom
time exposure for a PPO2level of 1.6 is 44 minutes. Once you reached 33 minutes of
bottom time with a PPO2 of 1.6, this alarm would be issued since 33 minutes is 75%
of 44 minutes. At a PPO2of 1.5, this alarm would be issued at 82.5 minutes, etc.
NOTE: While all other audible alarms of the dive computer consist of five long
beeps, the toxicity audible alarm consists of short double-beeps that sound for five
seconds.
WARNING: It is possible in certain diving circumstances to reach an Oxygen Toxic-
ity limit well before reaching a no-decompression limit. For this reason, NITROX
diving should only be conducted by a diver who has successfully completed a
sanctioned NITROX diving course from a recognized certifying agency.

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Installation
The Tank Unit (TU) high-pressure sensor installs into a high-pressure port of your
first-stage regulator. This should be done by your Authorized Dealer at the time of
purchase. Should you choose to install the TU yourself:
1. Remove your current high-pressure hose or the high-pressure plug from your first
stage regulator.
2. Lightly lubricate the sensor o-ring only with a lubricant approved for use with
EnrichedAirNitrox equipment. DO NOT USE SILICONE GREASE.
3. Screw the sensor, HAND TIGHT, into the first-stage high-pressure port
4. Using a 9/16" open-end wrench, "snug" the high-pressure transducer connection
taking caution to not overtighten.
CAUTION: DO NOT use your hand to tighten the high-pressure connection. This
procedure should only be accomplished by using an open-end wrench placed over
the metal nut of the high-pressure connection. It must not be overtightened.
With the first stage properly attached to a filled SCUBA cylinder, slowly open the cylin-
der valve. Once the valve has been opened, listen to the TU’s high-pressure connec-
tion for any escaping gas. If possible, completely immerse the tank and regulator in
water to see if bubbles form around your connection. If any gas leak is seen or heard,
immediately turn the gas off by closing the cylinder valve and take the entire regulator
system to the place where your purchased your NEMESIS™ IIa NITROX.
The Tank Unit (TU) clips to a low-pressure hose close to the first-stage. When clip-
ping the TU onto the low-pressure hose, a rolling motion will provide better results
rather than pushing the TU straight down onto the hose. The Wrist Unit (WU) may be
worn on the wrist or attached to your Buoyancy Control Device.
Activation
The TU will automatically activate when it senses a cylinder pressure greater than 200
psi or it may also be manually activated by tapping on the TU case in the circle area
that says "PWR" for approximately three seconds. Should you choose this manual
method of activation, it must be understood that the tapping should be performed in a
manner that produces sound rather than vibration. When tapping, you should use
your fingernail, coin, or other hard object that will produce sound when tapped against
the TU case. In general, using your fingertip will not provide the necessary sound to
successfully complete manual activation. The TU will issue five beeps as it begins its
activation sequence.
NOTE: If the TU is in the Altitude Adaptation Mode, four beeps instead of five beeps
will be issued.
It is also required that the TU be no deeper than 3 feet of water in order to activate.
Should you be deeper than three feet and attempt to activate the TU by using either
cylinder pressure or manually via tapping, the TU will not turn on. You must ascend to
a depth less than three feet and re-initiate the activation sequence.

14
You cannot manually turn the TU off. The TU will turn off:
1. After 15 minutes if no tank pressure is sensed and no dive is made.
2. After all 12 half-time compartments are completely "off-gassed"
on repetitive dives.
During an extended surface interval, the TU will enter a "sleep" mode to conserve
battery life. After a dive, your NEMESIS™ IIa NITROX will enter its sleep mode after a
surface interval of 40 minutes. During this sleep mode, all off-gassing calculations
continue and current surface interval and time to fly can be viewed by activating the TU.
Once awakened from its sleep mode, the TU will remain on for one hour before re-
entering the sleep mode. This assumes, of course, that no repetitive dive is initiated
between each wake-up.
The WU is activated by rotating tapping on the lower left corner of the face of the unit for
approximately five seconds or until the display becomes active. Since care has been
taken to reduce the occurrence of the WU being accidentally activated during trans-
port, the WU must be tapped for a longer period of time than is required to manually
activate the TU. This same rotating or tapping action is used to select the alternate
display. The alternate display is shown for three seconds before returning to the
normal display. The optional TACLITE, the active backlighting for the WU display, is
also activated whenever the alternate display is selected. TACLITE will remain illumi-
nated for approximately 10 seconds. If your WU does not have TACLITE, you can
contact your Authorized Dealer for an upgrade.
Since all diving calculations are made by the TU, it is possible to activate the WU
underwater should you mistakenly forget to do so prior to the dive. Once activated, the
WU will immediately display the current diving data being calculated by your TU.
During the dive, it is not possible to turn the WU off.
Once back on the surface, you can manually turn the WU off. This is recommended as
a battery saving measure since all calculations are being performed by the TU. To turn
the WU off on the surface, continuously tap the WU, in the same manner as that used
to activate the unit, until the display goes blank. With a little practice, you will be able to
tell just how many of your "taps" are required to turn the WU off.

15
OPERATING MODES
Self-Diagnostic Mode
At turn-on, both the TU and WU complete self-diagnostic tests before displaying cur-
rent information. During these tests, all of the legends and digits on the WU illuminate
for approximately five seconds. Upon completion, your computer enters the Surface
Mode.
Fig-1
Self-Diagnostic Mode
Explanation of Page Layouts
The following pages provide a "snapshot" of the screen displays for each of the
computers various functional modes, showing:
1. An illustration of the WU display
2. The LEGEND displayed
3. The MEANING of that legend
4. The VALUE depicted under that legend
5. The PAGE where you may find more information on that particular function.
Any WARNINGS or NOTES about that mode will be displayed on this page.

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Surface Mode
At the completion of the Self-Diagnostic Mode, the NEMESIS™ IIa NITROX enters the
Surface Mode. The Surface Mode has two displays: a Main Display and an Alternate
Display. You may switch to the Alternate Display by rotating the wrist quickly or tapping
firmly on the face of the WU. The Main Display shows: DIVE number, time-to-FLY,
TEMPerature,SURFace time,TANK pressure,and MAXimumDEPTH(of thelast dive).
The Alternate Display shows the last dives BOTTOM time, and breathing parameter
(BP). The following sample displays are of the Surface Mode.
FIG-2
Main Display
Approximately 10 seconds after powering up, your dive computer enters the Surface
Mode.
LEGEND MEANING VALUE SHOWN PAGE
DIVE dive of the day 2 35
FLY time-to-fly 15 hours 38
TEMP present air temperature 73 deg. F 37
SURF present surface time 0:20 minutes 37
TANK current tank pressure 3024 psi 37
MAXDEPTH maximum depth of previous dive 118 feet 35

17
Surface-Mode
FIG-3
Alternate Display
LEGEND MEANING VALUESHOWN PAGE
BOTTOM bottom time of last dive 1:26 (1hour 26 minutes) 33
BP ending breathing parameter 33 34
of last dive

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Predive Prediction Mode
FIG-4
Main Display
Afterone minute ofSurfaceMode, thedivecomputer will automaticallyenterthe Predive
Prediction Mode. During this mode, predictions of no-decompression limits (NDC) or
air time remaining (whichever is the lesser) will be made in ten foot increments
beginning at 30 feet and ending at a depth having at least two minutes of NDC time
available, up to a maximum predicted depth of 160 feet. The maximum depth pre-
dicted can be extended up to 320 feet in 10 foot increments via the optional Analyst PC
Interface. There is only a Main Display in this mode. The WU will display the DEPTH,
TANK pressure, and the lesser of the NDC (no-decompression time) or AIRtime
remaining for that depth.
LEGEND MEANING VALUESHOWN PAGE
REMAINTIMENDC remaining NDC time 2:17(2 hours 17 minutes) 36
TANK tank pressure 2176 psi 37
DEPTH predicted depth 40 feet 35
NOTE: If the cylinder pressure is less than 500 psi at the time the predic-
tions are being made, all predictions will reflect NDC times only.
Thefollowingchartdisplaysthe beginning,sea-levelno-decompressiontimesfor
thedepthsfrom30to 160 feetfortheU.S.Navy, DSAT, and the NEMESIS™IIa
Nitrox based on air as the breathing gas.

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Beginning NDC Limits
BEGINNINGNO-DECOMPRESSION LIMITS (INMINUTES)
DEPTH U.S. NAVY DSAT NEMESIS™ II NITROX
30 FEET ——— ——— 262
40 FEET 200 140 137
50 FEET 100 80 78
60 FEET 60 55 56
70 FEET 50 40 39
80 FEET 40 30 30
90 FEET 30 25 23
100 FEET 25 20 18
110 FEET 20 16 13
120 FEET 15 13 11
130 FEET 10 10 9
140 FEET 10 8 8
150 FEET 5 —— 7
160 FEET 5 —— 6
CNS/OTU Toxicity Display
At the conclusion of the Predive Prediction Mode, your dive computer will display the
current Central Nervous System (CNS) Toxicity and Oxygen Tolerance Unit (OTU)
Toxicity levels. The CNS and OTU levels will be displayed in percent. This screen will
be displayed for three seconds. There is only a Main Display for this mode.
FIG-5
Main Display
LEGEND MEANING VALUESHOWN PAGE
REMAINTIMENDC used to identify the 2:00 36
CNS/OTU Toxicity Display
TANK indicates the CNS 27% 37
Toxicity percentage.
DEPTH indicates the OTU 8% 35
Toxicity level percentage.

20
O2Mix Display
Following the CNS/OTU Toxicity Percentage Display, the current oxygen percent-
ages for Mix 1 and Mix 2 are displayed as a factor of 10. For example, an oxygen
percentage of 35.5 would be displayed as 355.
Mix 1 will be displayed under the TANK legend and Mix 2 will be displayed under the
DEPTH legend. This mode has only a Main Display and is displayed for three sec-
onds.
FIG-6
Main Display
LEGEND MEANING VALUESHOWN PAGE
REMAINTIMENDC used to identify the 1:00 36
O2Mix Display
TANK indicates the Mix 1 O221.5% 37
percentage times 10.
DEPTH Indicates the Mix 2 O262.5% 35
percentage times 10.
Your dive computer has the ability to enter O2percentages in 1/10 of a percent incre-
ments via the Field Programmer, or the optional Analyst Personal Computer Inter-
face. The WU displays these values as whole numbers. Therefore 28.7% O2would
be displayed as 287 on the WU.