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I am still recovering from the shock and horror following my
inspection of the electronically controlled UT rebreather system. If the
designer of this device worked in a regulated industry, where design safety,
performance validation and operational verification are a mandatory
requirement, this individual would either be dead or in jail. There are so
many flagrant violations of electrical safety and common sense I don't know
where to begin listing them. It appears to me that the designer of the
embedded microprocessor based control system was probably a programmer cum
engineer who got his training from Popular Electronics or Lance Levanthal's
cookbook series sold through Radio Shack.
This arrogant moron has put his "hi tech" surface mounted printed circuit
board (PCB) directly into the breathing loop (yes..right smack in the middle
of the counterlung assembly). The PCB is directly exposed to the moist
breathing gas. Imagine taking your personal computer under water with you
in a plastic bag, breathing on it continuously and then expect it to work.
Now imagine that your PC is part of your life support and is controlling the
oxygen content of your breathing gas. Now, how do you feel? The designer,
possibly aware that this wasn't too smart, had slopped RTV over the ROM
chip, hoping that perhaps this would afford some extra protection. This is
like bungee jumping with a rabbits foot. Most all of the control surfaces
were exposed to moisture and conductive leakage. Even a minor address
fault in a microcontroller can cause a program crash with potentially fatal
consequences. Bear in mind that the program is sensing, displaying and
controlling PPO2.
I have witnessed many "low voltage" battery operated circuits fail under
routine circumstances. The release of highly toxic smoke from burning
resistors, capacitors and plastic wire insulation that follows circuit
faults is quite amazing. If an electrical fault occurred during routine
operation, the resulting smoke from this fault would be subject to
inhalation by the diver and could easily be fatal. This is totally
unacceptable and would be disallowed by any international electrical safety
standards agency such as TUV, UL or CSA.
These rebreathers were being used in salt water, which can cause
catastrophic damage to electrical circuits given even minimal exposure. To
make matters worse UT had placed the NICAD battery pack within the breathing
loop. This is unbelievable stupidity. In the event of a loop flood the
batteries could and probably would rupture releasing cadmium compounds into
the divers inhalation stream. Cadmium is highly toxic and should be
strictly isolated from any physiological contact. The diver would get a real
"caustic cocktail" besides the standard dose of scrubber material.
The nicad batteries were being charged from standard 12 volt dc supplies and
not the required deltaV charging circuit available at any hobby store.
Thus, the nicads were probably being dangerously overcharged and were no
doubt already spewing caustic cadmium compounds into the system. Another
example of either nickel rocketry or stupitity or both.
A set of 3 five-conductor female connnectors provided the control ports to a
display system and external computers. The connectors were not marked or
polarized so that any mating connector could be inadvertently plugged into
any of the three females causing who knows what electrical damage.
The designer, perhaps fearing that this ridiculous system might be copied,
has blacked out the reference designators on all of the chips. This is like
painting a dive rite light black to prevent it from being reproduced. The
whole system was so kluged and bogus it is almost an after thought to
comment on the poor placement of the oxygen sensors (it did have the
obligatory three), and to immediately deduce that the "engineer" on this
unit had either failed or failed to take high school physics.
Obviously, rule #1 one was being violated here so all of the other compound
violations were almost immaterial. I did notice that the
designer/programmer/compugeek was making "inline" changes to the controller
program code. This explains the NOVRAM (non volatile ram used for program
and data storage). Not only was the physical engineering comletely half
baked and half finished, but so apparently was the firmware for the O2
(poison) control system. I am sure that the designer was very proud of
himself for using the latest in techno geekery "on the fly" firmware
modification capability. Like everything else on this system you can be
certain that the software had been subject to no validation or fault
testing. (Why bother when it's only a life support system)
Come to find out, these rebreathers were being used on unwitting human test
subjects. Fortunately for the subjects most of the devices were OBFs (out of
box failures). This is criminally irresponsible, and I was not suprised to
find out that the same people have been attempting to market this device for
twelve years under three labels. 12 years and still programming?
If you are in the market for a reabreather, I suggest that, in keeping with
Rule Number One, you avoid strokes , charlatans, bullshitters, 12-years and
no-product scumbags, and ask somebody who knows what the fuck they are
talking about, and you will not find such a person in the recreational dive
industry.
Military and commercial engineers figured this stuff out a long time ago,
and these clowns do not have access to that information (or are too arrogant
to use it), and are betting YOUR life on it, and letting YOU pay for it. Now
who is a dumb fuck?
Your Friend, TRIMIX
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