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The relative and absolute performance of 4 dive computers on a controlled bounce dive to 50 m (on air).

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Abstract

The relative and absolute performance of 4 dive computers on a controlled bounce dive to 50 m on air: 4 standard dive computers (Scubapro G2, Aladin TEC 2G, Ratio iX3m and Cochran EMC-20 H) are compared relative to each other and with well-tried air diving tables like: United States Navy USN old 1990, USN new 2018, DCIEM 1992, DRÄGER 1984 and Deco 2000. The question: do the advertised conservativism settings of the G2 & iX3MDeep match any standard procedures? Say, for eg. with regular Gradient Factors? is tried to answer with a benchmark of ubiquitious desktop deco software (GUE DecoPlanner 3 and DIVE Version 3) and a comparison with box/square profiles of the above cited air diving tables.
The relative and absolute
performance
of 4 dive computers on a
controlled bounce dive (*) to
50 m @ air
1
(*) HBO center Stuttgart
02/08/2020
2
Relative Performance:
comparison of the
TTS / stop times (*)
of the 4 computers
relative to each other
Absolute Performance:
comparison of depth readings
with HAUX systems
and TTS / stop times with
well-tried air diving tables
(*) TTS = time-to-surface,
i.e.: sum of all stop times + (bottom depth / ascent rate)
3
HBO cente
r
Stuttgart
4
Question:
do the advertised
conservativism settings
of the G2 & iX3MDeep
match any standard
procedures?
(say, for eg. with regular
Gradient Factors?)
5
Evaluated with:
DecoPlanner 3.1.4
&
DIVE Version 3_07
older english version there:
https://www.divetable.info/DIVE_V3/V3e/index.htm
6
Standard Air Tables
(for comparison with
square / box profiles):
DCIEM Air Diving Tables;
Defence and Civil Institute of Environmental Medicine, c.e. 1992
DCIEM No. 86-R-35, page 1B-16
Deco 2000; Dr. Max Hahn, c.e. 2000
US Navy Diving Manual, Revision 3, 0927-LP-001-9010,
15 February 1993, page 9-60
US Navy Diving Manual, Revision 7, 0910-LP-115-1921,
30 April 2018, page 9-81
Dräger Austauchtabelle #210, Dezember 1984, p. 9
(still used as MDv 450/1 in the german navy, p. A 6-7)
Bounce 50 m / 8‘ @ air
7
The 4 computers:
Bounce 50 m / 8‘ @ air
8
The 4 computers:
from left to right
Scubapro Aladin TEC 2G
Software Version: 40 20 72 73 25
Setting: MicroBubble Level L0
Scubapro Galileo G2
HW: 0.0
SW: 1.5
Setting: MicroBubble Level L1
Cochran Undersea Technology EMC-20 H
Setting: Con = 50 (i.e. maximum conservatism)
DiveSystem / RATIO iX3M Deep
Software: 4.0.70 / 014
Setting: PS = 1 (i.e.: GF Hi = 0.9, GF Lo = 0.9)
Bounce 50 m / 8‘ @ air
9
The profile: G2 in log book mode
Bounce 50 m / 8‘ @ air
10
The profile:
G2 with software LogTRAK 1.7.0.1
Bounce 50 m / 8‘ @ air
11
The profile: Ratio iX3M in log book mode
Bounce 50 m / 8‘ @ air
12
The profile: iX3M with
software
Subsurface 4.9.3
Bounce 50 m / 8‘ @ air
13
The protocol from the deco chamber dive:
Bounce 50 m / 8‘ @ air
14
Analysis of the deco chamber profile:
bottom phase 8 min
deco stops @: 9 m / 5 min 6 m / 5 min 3 m / 15 min
deep stop @ 21 m / 2 min
Ascent Rate: (50 – 21)/4 = 7.25 m/min
Ascent Rate = (21 – 9)/3 = 4 m/min
Planned TTS :
4 + 2 + 3 + 5 + 5 + 15
= 34 min
worst case scenario: 6 + 8 + 4 + 2 = 20 min bottom time for conservative table planning (box profile)
realistic scenario: 6/2 + 8 + 4/2 + 2 = 15 min bottom time for liberal table planning (box profile)
Bounce 50 m / 8‘ @ air
15
Comparison with DP 3 at 50 m:
GF 100/100 GF 0.9 / 0.9
Comparison with DIVE V 3_07 at 50 m:
GF 100/100 GF 0.9 / 0.9
The delta t between DP3, DIVE and the G2 stems from a different ascent rate:
DP3 can use only one full integer, whereas DIVE and the test profile in the
HAUX chamber used 2 ascent rates: 7.25 and 4.0 m/min;
G2 uses 6.85 m/min in planning mode.
Bounce 50 m / 8‘ @ air
16
Comparison with DP 3 after deep stop 21 m 2 min:
GF 100/100 GF 0.9 / 0.9
Comparison with DIVE V 3_07 after deep stop at 21 m / 2 min:
GF 100/100 GF 0.9 / 0.9
Bounce 50 m / 8‘ @ air
17
Comparison with other tables / worst case scenario:
Table
Name Para-
meters Stoptime
@ 12 m
[min]
Stoptime
@ 9 m
[min]
Stoptime
@ 6 m
[min]
Stoptime
@ 3 m
[min]
TTS
[min]
DRÄGER 51 m
20 min -551530
DCIEM 51 m
20 min 5 5 8 20 43
Deco
2000 51 m
18 min 2 4 7 14 32
USN old 51,8 m
20 min - 4 15 25
USN new 170 feet
20 min 3 6 24 38
Bounce 50 m / 8‘ @ air
18
Comparison with other tables / realistic scenario:
Table
Name Para-
meters Stoptime
@ 9 m
[min]
Stoptime
@ 6 m
[min]
Stoptime
@ 3 m
[min]
TTS
[min]
DRÄGER 51 m
15 min - 5 10 20
DCIEM 51 m
15 min 5 7 10 27
Deco
2000 51 m
14 min 34921
USN old 51,8 m
15 min -2513
USN new 170 feet
15 min - 3 13 22
Bounce 50 m / 8‘ @ air
19
Comparison realistic scenario:
G2 @ L1 planner fits box profile with:
Bühlmann Table correction factor
GF Hi = GF Lo = 0.85
and Aladin @ L0
Bounce 50 m / 8‘ @ air
20
G2 warnings:
Ascent Rate exceeded
MicroBubble Level
reduced from L1 to L0
due to the missing 2 min stop
@ 3m
(heart rate monitor
& tank pressure not used)
Bounce 50 m / 8‘ @ air
21
The others:
Aladin Log Book
EMC-20H Log Book
Bounce 50 m / 8‘ @ air
22
Synopsis:
The errors in the depth-reading range from ca. 2.5 to 6 % which is regularly
more than the specifications from the dive computers handbooks.
The EMC-20 H (with Con = 50 ) matches, just by accident, the
Aladin TEC / L0, which is funny, since neither the intended user-groups
(pro vs. rec) nor the used deco models (modified USN with 20 compartment vs.
modified Bühlmann ZH-L with 8 compartments) match.
Aladin TEC / L0 matches pretty much the benchmarks with the claimed
Gradient Factors = 1.0, i.e.:
100 % ZH-L with Bühlmann Table correction factor.
The Ratio iX3M with PS =1 matches pretty much a standard conservatism
with the claimed Gradient Factors of 0.9
The G2 with L1 matches pretty much with a standard GF of
GF Hi = 0.85 & GF Lo = 0.85, but only in the
„Dive Planner“ mode for a square / box-profile.
Bounce 50 m / 8‘ @ air
23
Synopsis, G2 continued:
During diving it doesn‘t match at all:
there is an added conservatism through a hidden / unpublished
parameter / procedure, which presents itself to the diver
during ascent as an unsymmetrical de-saturation, i.e. prolonged stop times.
This may not stem from the heart rate nor the air consumption
or temperature adaptions in the modified ZH-L implementation,
since these features have not been used during the test dive.
But the de-sat times during surface interval match again with other
computers:
SI ca. 24 h
This asymmetry in de-saturation reveals itself only if MB Level > 0, i.e.:
L1 or higher. With L0 this asymmetry is not seen (page 4):
https://www.divetable.info/skripte/HBO_Stgt_250519.pdf
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