Appeared in DIVER September 2008

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John John Bantin has been a full-time professional diving writer and underwater photographer since 1990. He makes around 300 dives each year testing diving equipment.

COMPUTER SEEMANN XP5

THERE SEEM TO BE TWO TYPES OF DIVER in this world. There are those for whom the sheer technicality of diving is important and for whom the pinnacle of achievement would be
to descend a line to a deeper point than anyone else has been. Then there are those who simply want to go somewhere nice and swim about with the fishes, looking at whats there.
Divers in this second group dont want to be bothered with SACs and gradient factors. They want a computer that tells them how to stay safe from decompression illness.
It might surprise the dedicated British technical diver that these people represent the great majority of divers in the world, and without them to give volume to the diving market, all that tekkie gear would be very expensive short-run prototypes.
One of the best-selling diving computers in the USA does exactly what this type of diver wants, and the new XP5 from Seemann is very reminiscent of that product.
Even the packaging promises no compromise but simplicity. Strap it on and go!
In fact, it is a peculiarity of world trade that one US giant diving-equipment manufacturer makes this computer for a small European brand that is owned by a rival American manufacturer.
The Seemann XP5 is operated by two buttons. One is under the display, the other
at the side. You use these initially to set up the computer.
The instruction booklet is very easy to follow. Once the main details such as time and date, metric measurements and the alarms you might want to include have been entered, the only setting you then need to make regularly is to match the computer to the nitrox mix you are using.

Algorithm
For those who like to know such things, the decompression model for the XP5 is based on the no-decompression multi-level repetitive dive schedules tested by Drs Ray Rogers and Michael Powell. These tests did not include dives deeper than 27m.
Decompression dive predictions are based
on US Navy theory, and adjusted to be more cautious. For example, the XP5 gives 19 minutes of no-stop time at 30m, whereas the US Navy tables give 25 minutes.
From this, one could deduce that the XP5 is aimed at divers who rarely go deeper than the recreational limits set at most dive locations, and do not intend to do deco-stops.
Neither are these divers likely to be as young and fit as any US Navy personnel.

Display Legibility
The remaining no-stop time is the information displayed in the largest figures. Then there is the actual depth, the maximum depth achieved and the dive time. A graphic indicates your nitrogen loading as it builds up, and another indicates your ascent rate. Naturally, I never saw a too-fast ascent-rate warning.

Settings
If you use the XP5 in nitrox mode, as most divers will, it defaults to a worst-case scenario 50% O2 after each dive. This would be very irritating
if doing a series of dives, but you have the option to switch this function off. I did.
The backlight can be set to stay on for up
to seven seconds.
Most divers want water activation. They dont want to have to remember to switch on their computer immediately before entering the water. You can turn off the water-activation function, but I cannot imagine wanting to do so.

In The Water
The no-stop time is clearly displayed, and there always seemed to be lots of it once I returned to, say, 15m or less. In fact, there was almost twice as much on the XP5 at times as was displayed on both the Uwatec (L1) and Suunto (RGBM 100) computers that I wore alongside it.
I was diving with Bret Gilliam, the founder of TDI and a true diving pioneer. He and I both reflected that computers of the type that includes the XP5 were good for the sort of diving we were doing (shallower than 25m), but put them into decompression-stop mode and the results can be punishing. They seem to have a Jekyll & Hyde character.
Bret told me of one incident in which a woman was still hanging on the deco bar of the boat with one of this family of computers when he was going in for his next dive! So if you get an XP5, remember - its an entry-level computer meant for use on entry-level dives.

OTHER COMPUTERS TO CONSIDER:
Suunto Gekko, £185
Oceanic Veo, £185
Aladin Prime, £235


Divernet Divernet
PRICE £179
NITROX 21-50%
GAUGE MODE Yes
FAST ASCENT WARNING Yes
OTHER WARNINGS Max depth, Dive time, Deco dive time
NORMAL IN-WATER DISPLAY Depth, Dive time, No-stop time remaining, Max depth
ALTERNATIVE DISPLAY 1 + time and temperature
ALTERNATIVE DISPLAY 2 + current ppO2 value
DECO INFO Total ascent time, Stop depth, Depth
DEEP STOPS No
SAMPLING RATE every 2, 15, 30, or 60sec
ALTERNATIVE SAMPLING DEPTHS 0.5, 1.5, or 3m
DIVE PLANNING No stop times
LOGBOOK 24 dives
PC INTERFACE Yes
MODES Air, Nitrox, Gauge
BATTERY User-replaceable CR2450
CONTACT www.seemannsub.net
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