Specifications

32
Wisdom 3 DC Manual
© 2002 Design, 2011 Doc. No. 12-5274-r01 (8/31/11)
PSI
FEET
NITROX
O2
N2
SAFE
MINUTES
TIME
DIVE
FEET
MAXIMUM
PSI
FEET
NITROX
O2
N2
TIME
SAFE
MINUTES
G


PSI
O2
N2
FEET
TIME
SAFE
MINUTES
NITROX
PSI
FEET
TIME
DIVE
FEET
MAXIMUM
NITROX
O2
N2
SAFE
MINUTES
PSI
FEET
TIME
DIVE
FEET
MAXIMUM
NITROX
O2
N2
SAFE
MINUTES
G
A
S
DIVE TIME REMAINING (DTR)
One of the most important pieces of information on Sherwood dive computers is the 'Dive Time Remaining
numeric display'. The Wisdom 3 constantly monitors No Decompression status, Oxygen Accumulation, and
Air Consumption Rate.
The Dive Time Remaining (DTR) display will indicate No Deco Dive Time Remaining (NDC), Air Time Re-
maining (ATR), or O2 Dive Time Remaining (OTR), whichever time is the least amount available.
• When NDC is displayed as DTR on the Main (Fig. 60a), ATR is displayed on ALT 1 (Fig. 61a).
• When ATR is displayed as DTR on the Main (Fig. 62a), NDC is displayed on ALT 1 (Fig. 63a).
• When OTR is displayed as DTR on the Main (Fig. 64a), ATR is displayed on ALT 1 (like Fig. 61).
No Deco Dive Time Remaining (NDC)
No Deco Dive Time Remaining is the maximum amount of time that you can stay at your present depth be-
fore entering a Decompression situation. It is calculated based on the amount of Nitrogen absorbed by hypo-
thetical tissue compartments.
The rates each of these compartments absorb and release Nitrogen is mathematically modeled and compared
against a maximum allowable Nitrogen level. Whichever one is closest to this maximum level is the con-
trolling compartment for that Depth. Its resulting value will be displayed numerically along with the SAFE
MINUTES icon and graphically as the Nitrogen Bar Graph.
As you ascend from Depth following a dive that has approached the No Decompression Limit, the
Nitrogen Bar Graph will recede as control shifts to slower compartments. This is a feature of the
Decompression Model that is the basis for Multilevel Diving, one of the most important advantages
that Sherwood dive computers offer.
The no decompression Algorithm is based upon Haldane’s theory using maximum allowable nitrogen levels
developed by Merrill Spencer. Repetitive diving control is based upon experiments designed and conducted
by Dr. Ray Rogers and Dr. Michael Powell in 1987. Diving Science and Technology
®
(DSAT), a corporate
afliate of PADI
®
, commissioned these experiments.
O2 Dive Time Remaining (OTR)
Oxygen Accumulation (saturation or exposure) during a dive, or 24 hour period, appears graphically as the
Oxygen Accumulation (O2) Bar Graph. As time remaining before reaching the Oxygen Exposure Limit de-
creases, segments are added to the O2 Bar Graph (O2BG).
When the amount of time remaining before reaching the O2 Limit becomes less than the NDC, calculations
for that depth will be controlled by O2. OTR will then appear as DTR on the Main. As O2 accumulation
continues to increase, the O2 Bar Graph will enter the Caution Zone. If OTR continues to decrease, the
O2BG will enter the Danger Zone and the full O2BG will ash.
Air Time Remaining (ATR)
The Wisdom 3 calculates ATR using a patented algorithm that is based on a diver's Air Consumption Rate and
current depth. Tank pressure is measured once each second and an average rate of consumption is calculated
over a 60 second period. This rate of consumption is then used in conjunction with a knowledge of the depth
dependence to predict the Air required for the diver to make a safe controlled ascent including any required
Decompression Stops.
Air Consumption and Depth are continuously monitored and ATR reects any change in circumstances. For
example, when you suddenly nd yourself swimming against a strong current and begin breathing more rap-
idly, the Wisdom will recognize the change and adjust the ATR accordingly.
Remember, ATR is the time you can remain at your present Depth and still surface with the Tank Pressure Re-
serve that you selected during setup (End Pressure Alarm Set Point).
When ATR (Fig. 62a) decreases to zero, you should immediately initiate a controlled Ascent while monitoring
your Tank Pressure. However, there is no reason to panic, the Wisdom 3 has allowed for the Air necessary for
a safe ascent including any Decompression Stops required.
Fig. 60 - Dive Main
(DTR is NDC)
a
Fig. 64 - Dive Main
(DTR is OTR)
Fig. 62 - Dive Main
(DTR is ATR)
Fig. 61 - Dive Alt
(if NDC is on Main)
Fig. 63 - Dive Alt
(ATR is on Main)
a
a
a
a