Stphen wrote,

> 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.


I don't know a lot about this type of meter, I had only see pictures of
one until recently, when I saw a real one, it was bigger than I thought.

AFAIK the unit is basically a mechanical pressure gauge with a compressable
bag attached to it. Between the two is a mechanical resistor (ceramic, I
think).
This is permiable to air, but at a fixed rate.

As you take the unit into water, the pressure acts on the compressable bag,
this forces air
through the resistor. This in turn causes the meter to register.
Obviously you can see that the amount that the meter will register will
depend on the depth (ambient pressure)
and the time, until an equilibrium is reached.

As you surface, air will be forced back from the gauge side, through the
resistor, hopefully giving some indication
of the inert gas loading. Ha ha.

I've never seen an instruction manual for one, so I don't know if you were
supposed to ascend in stages according to the meter, or use a fixed ascent
rate or what.

The rate of gas transfer through the resistor varied greatly with
temperarture and apparently from unit to unit.

I beleive that it earned itself the name 'Bend-o-matic' :-)

hth
Paul

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