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On the reliability of dive computer
generated run-times, Part IX:
G2 TEK Altitude Adaption
Abstract:
Here, in Part IX, we performed an extended altitude test with the highly topical
SCUBAPRO / Uwatec mix-gas dive computer Galileo 2 TEK / „G2 TEK“
along the Galileo G2 with new firmware and a SHEARWATER PERDIX
with the DCIEM software-option. This extended test entails simulated dives
at a ca. altitude of 2.200 m above SL during 10 min., 1 h and 2 h adaption
phases to the reduced ambient pressures.
Introduction: slide # 3
Methods: slides # 4 & 6
Results: slide # 7
Data: slides # 8 11
Discussion & Conclusion: slide # 12
References: slide # 13
3
Introduction:
Scuba diving at altitude, i.e. at reduced ambient pressure,
requires adapted diving-procedures and –tables. These procedures & tables
are regularly derived from those at sea-level (SL), that is, at an altitude of
ca. 0 m above SL.
There are many of those procedures available: these differ in the methods of
extrapolation of the maximal allowed or tolerated compartment (tissue-)
inertgas partialpressure from SL, i.e. at Pamb (ambient pressure) of ca. 1 Bar,
to the reduced Pamb at altitude. The outcome is usually a reduced NDL („no
decompression limit“) in comparison to SL procedures resp. longer stop-times
at the various stop-depths and, depending on Pamb, a shift of the last 2 deco-
stop depths from 6 & 3 m to 4 & 2 m, respectively.
An outline of these procedures, along with a comparison of published, printed
altitude tables is described in [1].
4
Methods (1):
We simulated our notorious test-profile (42 m bottom depth,
25 min bottom time, with air as breathing gas and water density set to: “Fresh“)
at the reduced ambient pressure in the passengers cabin during various
intercontinental flights from Zürich to Tel Aviv with commercial, civilian air-
planes. These parameters have been fed into the planning mode /
dive simulation interfaces of the computers, with the results
on slide # 7.
No user adjustable conservativism factors have been used. Both G2 were set
to a MicroBubble Level of 0 (MB Lvl = L0), whereas the G2 TEK was set to
a pair of symmetric Gradientfactors GF High = GF Low = 1.0 (= 100 %).
The measured cabin-pressures were read by the dive computers after ca. 10
min, 1 h & 2 h into the flight, i.e. after reaching the final, cruising height of ca.
33.000 feet. The readings for this topical test were ca. 770 +/- 10 mbar,
equivalent to an approximate altitude of ca. 2.200 to 2.500 m above SL (details
pls. cf. DATA section). The dive computers calculated TTS are then compared
to each other and with the ZH-86 air decompression table for an altitude of
700 – 2.500 m above SL from A. A. Bühlmann (pls. cf. slide # 7).
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Methods (2):
The used dive computers were, from left to right:
SCUBAPRO (Uwatec) Galileo 2, „G2“;
Hardware: 0.0, Software Version: 2.0
SCUBAPRO (Uwatec) Galileo 2 Tek, „G2 TEK“;
Hardware: 1.0, Software Version: 1.0 (blue frame cover)
SHEARWATER PERDIX, Firmware v87 / BT10, Hardware: SA-02A,
Deco Model: DCIEM
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Sample of Dive Planner Menu / G2 TEK:
bottom depth: 42 m; fresh water;
bottom time 25 min @ Air:
TAT / TTS 32 min (V1.0) at Sea Level
with gradient factors: 100 / 100
Scubapro
G2 TEK:
Hardware Version 1.0
Software Version 1.0
per 07/2022
(*) TAT = TTS: time-to-surface =
sum of all stop times + ascent time (here ca. 6 min for the G2 TEK)
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Comparison of TTS in [min] for the test-schedule
bottom depth 42 m / 25 min bottom time @ Air
vs. the adaption times at altitude (Interval) of
10 min, 1h & 2 h:
Adaption
times 10 min 1 h 2 h
Computer ↓ TTS [min] TTS [min] TTS [min]
G2 TEK
(GF Hi = GF Lo =
1.00 = 100 %)
46 42 39
G2 V 2.0
(MB Level = L0) 63 57 53
PERDIX
(DCIEM option) 73 64 60
Table ↓
ZH-86
(@ 700 – 2.500 m)
42 m / 27 min
n.a. 44 44
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Discussion / Conclusion:
The resulting TTS (slide # 7) are somewhat more conservative than the
printed tables entries.
MB Level (= Micro Bubble Level) and Gradient Factors (GF) are proprietary
modifications of the tolerated compartment inertgaspressures, here they are
set = 0, resp. to 1.0 = 100 %. This implies that the original A.A. Bühlmann
ZH-L16 C values should be used. It seems, that they are not. If this stems
solely from modifications of the a-/b-coefficients or from further
modifications of other, pivotal parameters of the ZH-L framework,
is open to conjecture, since no complete documentation from the dive
computer manufacturers is publicly available.
This is as well reflected in other simulated dive scenarios @ SL and other-
than-Air breathing mixes [2].
Further comparisons with Air/EAN/Nitrox, Trimix, Heliox & Oxygen are
posted in the 2022-updates of the virtual dive computer museum [3].
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On the reliability of dive computer
generated run-times, Part IX
References:
[1] Rosenblat M., Vered N., Eisenstein Y., Salm A. (01.07.2022)
On the reliability of dive computer generated run-times,
Part VII; Altitude Test
DOI: 10.13140/RG.2.2.14589.64487
[2] Miri Rosenblat, TAU; Nurit Vered, Technion Haifa;
Yael Eisenstein & Albi Salm, SubMarineConsulting
On the reliability of dive computer generated run-times
27.07.2022, Part VIII: G2 TEK
DOI: 10.13140/RG.2.2.22374.50247
[3] the virtual dive computer museum:
https://www.divetable.info/museum_e.htm
