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Hi Stephen I have an old deco meter that sounds very similar to yours. This is how I think it works (i.e. don't quote me on this ;-). There is a gas filled bag connected to a bourdon tube that turns the needle (just like a mechanical depth gauge). Between the bag and the tube is a permeable ceramic block that allows gas to pass through it at a reduced rate supposedly emulating gas diffusion in and out of tissues. As the diver descends the ambient pressure squeezes the bag and forces gas through the ceramic block and into the bourdon tube that turns the needle. As the diver ascends the reverse happens. Most people (around here) used the meter to remain within no deco limits. This was done by terminating the dive as the needle approached the red. It could also be used to for deco. During deco dives the needle enters the red. The first bit of the red requires a 10ft stop and further into the red requires a 20ft stop. The diver ascended at 60 ft / min to 20ft and hung until the needle entered the 10 ft zone the he moved up for the 10ft stop until the needle left the red and he could surface. I think the earlier models used a cylinder of diatomaceous earth rather than ceramics. The manufacturers adjusted the permeability of the block by trimming the length of cylinder. Although this is a pretty scary concept these days thousands of incident free dives were carried out on these units ... of course they did bend a few too!! Kia Ora ..R From: "Stephen Kamarudin" <s.kamarudin@dm*.wa*.go*.au*> To: techdiver@aquanaut.com Date sent: Tue, 21 Sep 1999 15:23:32 +0800 Subject: Antique Diving Equipment > > > Hello Everyone > > I have only recently become interested in tech diving and appreciate the > information and discussions that everyone has contributed. > > The reason I am emailing is that I have an old mechanical decompression meter > (circa 1960's I think?) and would appreciate any information that anyone out > there in the techdiving world might have on this piece of equipment. I don't > intend to use it but it would be interesting to know how it was intended to > work. > > The unit is rectangular (about the size of 2 cigarette packets), made from > stainless steel with a round gauge on the front. The rubber wrist/arm strap as > with the rest of the unit looks in excellent condition. There are a number of > patent numbers on the unit for USA, Italy, Germany, Switzerland, France, Spain > and U.K. The words "Made in Italy" are written on the gauge face along with many > other numbers and graduations. A brand name "SOS" with a small lightening bolt > above the "O" also appears here. > > Before I go tracing back through patent numbers etc, can anyone help me. I > couldn't find anything on the net about a company called "SOS". > > Any help would be appreciated > > Thanks > > Stephen Kamarudin > Newby tech enthusiast > Western Australia > > > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver- request@aq*.co*'. Rod Budd National Institute of Water and Atmospheric Research Ltd. (NIWA) Gate 10 Silverdale Rd (PO Box 11-115) Hillcrest Hamilton New Zealand. +64 7 856 7026 business +64 25 734 066 mobile r.budd@ni*.cr*.nz* http://www.niwa.cri.nz/ -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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