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Jens, I
did not read through your earlier email carefully (didn’t have my mug of
morning tea yet) and unfortunately it is gone now. There are two types of
air/hydraulic column depth gages that I know of, one very simple and economical
and the other a little more involved but very dependable. I am not sure
where your Papenberg gage falls into these descriptions: 1.
Capillary
gage is a tube with one end closed and so arranged that a column of air is
trapped within. With an increase with depth the air column is compressed
but not linearly. At 33 fsw ( 2 atmos.) the column of air is ½ of its
original length, at 66 fsw the length is ⅓, 99 fsw the length is ¼, etc.
They are most accurate in shallow water and loose accuracy as you increase in
depth. They are subject to error from clogging of the inlet. 2.
The
pneumo-fathometer is used in the measurement of large tank levels and very
accurate determination of depth for commercial divers. Air is injected
into a tube (or hose in the case of divers) that is open to the sea at one end and
the pressure increased until it levels off. At this point the air is bubbling
out of the end of the tube and measuring this air pressure gives a direct
indication of depth. The measure of the air pressure still needs to have
care taken to insure the gage is measuring psia and not psig. We
get back to the argument of what is the minimal safe solution for the application.
After reading David’s last email that he qualified the depth gage as being
watch-styled and not necessarily embedded in a watch. If this is so, then
he may indeed be using a straight diving depth gage. These come in two
varieties (the capillary gages are no longer found generally due to the
accuracies and hazard issues associated with this type): there is the
electronic depth gage that depends on contact with water to be turned on and
remain operating in depth mode and there is the oil-filled Bourdon tube gage
(which measures psia). The Bourdon tube gage is economical, simple, dependable,
and readily available…this is what I would recommend for this
application. In addition, this analogue and very easy to read in many
more conditions than the electronic digital gage. Review
of the web finds little information on the Papenberg gage but several pages
concerning U-boats point to its use in determining the height of some other
area of the sub in relationship to the waterline. In particular it was
used to determine the height of the periscope. Would need more
information to make the determination of being atmospheric independent since it
was located in the Control Room of the sub which was at or near 1 atmosphere of
pressure. Looks
like the formal evacuation of the island was called off today so have to fly
back to Andros tomorrow. Ike veered further south and will be hammering
Cuba instead. R/Jay
Jay
K. Jeffries Andros
Is., Bahamas A
skimmer afloat is but a submarine, so poorly built it will not plunge… -----Original Message----- Jay I hope you do agree that the Papenberger is not a
differential type gauge. The way I see it, this hydraulic type gauge should be
quite independent from any local influences, i.e. from various local
atmospheric pressure conditions inside the boat. regards, Jens |