In dive, manage having EAN programed into computer while diving air?

[rmssetc]

@saridnour even on the LP side, you're talking ppO2 starting at 2.0 ish at the surface for air, and only goes up from there. The sensors we have are simply not capable of handling that. 2.0 at the surface, close to 3.0 at depth, just for air. Double that for EAN40. Simply not something the sensor technology can handle. Since the ppO2 is a function of IP, and no regulator is perfectly balanced to tank pressure, that sensor would also have to have a pressure sensor in it to normalize it.

Absolutely accurate, but perhaps you're overthinking it. Unlike a CCR, there's no need to measure the O2 percentage continuously during the dive. Imagine an AI computer that's got a small purge button -- either on the console (hose unit) or on the transmitter. Pressing the purge button -- while not submerged, please -- would divert air through a restricted orifice, then across an O2 sensor. The resulting O2 reading would be sent to the computer when the purge button is released. Bonus points for reading CO as well and popping up a "You Will Die" warning if it's over a set value (10PPM?)

The new computer+analyzer would be only slightly larger than a current console mounted computer (double the size of a transmitter, but the transmitter could be sold with an integrated short hose, using the same design for the hosed gas analyzer on a console).

PDC manufacturers could advertise this as the newest improvement in diver safety (particularly if there's CO measurement) and DMs would-wide would be stop having to tell customers how to set their own computer for Nitrox, and this would be great for gear rental packages.

Of course, this would also require a set of batteries separate from the computer or transmitter and a pressure resistant waterproof housing for the O2 & CO cells, but user accessible for [semi]-annual changes and a way to calibrate the cells without a stream of high-pressure air.

It'll never happen, at least not for less than the cost of a computer + 4 (5?) conventional nitrox analyzers.

 

[Wibble]

Issues...

• This would encourage numpties to ignore standard best practice of checking their gas and labelling their cylinders before connecting their regulators.
• Cells need regular replacement. Just why do rebreathers have three or more cells?
• Cells are fragile and can’t get wet.

 

[rmssetc]

Issues...

• This would encourage numpties to ignore standard best practice of checking their gas and labelling their cylinders before connecting their regulators.

You seem to be overlooking the original issue that prompted this whole thread.

@saridnour was aware that he was using air, and there was no problem with the cylinder label...but that information didn't get into his dive computer.

My largely facetious proposal about a gas analyzer integrated into a PDC would (1) make the practice of checking the gas mixture much easier and (2) eliminate the need for labeling in a single-cylinder recreational context.

• Cells need regular replacement. Just why do rebreathers have three or more cells?

• Cells are fragile and can’t get wet.

Keeping the cells dry is a solved problem, as shown in the use of cells in rebreathers. Not necessarily cheap/easy/maintenence-free, but solved.

 

[Wibble]

OK, as a thought experiment...

O2 cells are little batteries that generate small amounts of electricity relative to the amount of oxygen pressure; the higher the pressure, the greater the electricity generated. Like all batteries they run out of 'fuel' and need to be replaced when depleted. Unlike other batteries, O2 cells must be calibrated pretty much every time they’re used.

There is a considerable difference between using cells at ambient pressure and to lower oxygen concentrations, such as a surface Nitrox tester. These typically have a calibration knob to adjust the reading to 20.9% in air. They are used with a flow restrictor to prevent the pressure rising and inaccurate readings. Also, most nitrox is low concentrations of oxygen, below 40%. People who dive with high percentages, such as accelerated decompression diver have do take more care with calibration especially as cells reach the end of their lives as they get current limited.

Therefore your "requirements" for this nitrox integrated computer are...

• Utter simplicity
• Oxygen measurement at ambient pressure (to reduce cell loading)
• Automatic calibration
• Simple cell replacement
• Waterproof design (cells can't get wet and need to dry out)
  
• Slick design (there's no extra space as there is in rebreather heads)

All for a market of a few people. It won't be cheap :-(


Alternatively...

• The place selling nitrox has a measuring sensor, some masking tape and a marker pen.
• You buy the measurement sensor (~ £200/$200), the tape and pen
• And when you inevitably forget to configure the computer on the surface, you think it through; learn the lesson; and don't do it again!

 

[Atlantic Explorer]

For a recreational diver who is using a dive computer, tables are irrelevant especially if you are making a multi-level dive (vs. square profile). Try it, go to 30 meters with a dive computer and work your way up and do it another time using dive tables and your computer in gauge mode and see the difference in NDL's.

Dont think that’s what PfcAj was getting at

 

[Divrtim]

The difference between EAN of 30% and EAN 21%( air) is 9 torr. I would have just breathed the 30% during the whole dive. Increase of O2 equals decrease of N. 30% is safer than air except at 100 feet+.
The real issue left out in this thread is whether you had done multiple dives the day before or where carrying a residual N load and were planning to do another dive that day? If so, mapping your real time dive on the Navy table would give you the correct baseline of where you were at the end of the dive.
If you weren't diving again that day it doesn't matter. You computer would reset in 24 hours. The moral in your story is; "I forgot to check the setting (was in a hurry to hit the water) pre dive." Being in a hurry is the fastest way to being a fatality. In tec diving the surface becomes a ceiling. The most important piece of equipment you take on any dive is your own brain. No amount of redundant equipment will substitute for common sense.
ALL dive problems resolve easier on the surface. It'd better to be recompressed then dying decompressing.