[PSUBS-MAILIST] Mechanical Depth Gauges

[Alan via Personal_Submersibles]

Doug,
I am not sure how Snoopy's pressure gauge is set up but
I know of at least one person that has a rubber solder sucker filled 
with oil screwed ( or attached) to the outside of the gauge port.
The gauge then only sees oil not sea water.
Gauges with electronic displays & the ability to flick between metric,
imperial, psi, mpa etc are pretty cheap. I have a dwyer gauge ( somewhere).
   Being a young person you may want to go down the route of buying
a gauge that you can attach to an arduino, then electronically display on a 
board as big as you like! With a bit of code at the push of a button you
could get it to display fresh or salt water depth. 
Cheers Alan



Sent from my iPad

> On 31/07/2018, at 6:36 AM, Douglas Suhr via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> Ah, I think you're right Jon... because the gauge plate would not be
> pressured anyway, huh. Never thought of that.
> 
> No there was no gasket or anything, so I guess any moisture in the
> viewing portion of the gauge would just come from moisture inside the
> hull of the sub.
> 
> And thank you for the pressures... not a huge difference but I suppose
> at deep depths it could work out to be somewhat of an error.
> 
> I wonder how Alec printed such a nice looking label(?). ~ Doug
> 
> On 7/30/18, Jon Wallace via Personal_Submersibles
> <personal_submersibles at psubs.org> wrote:
>> Fresh water: .433psi per footSalt water: .445 psi per foot
>> If there was no gasket sealing the acrylic/glass cover and bezel then it's
>> likely condensation caused the wrinkling of the label.
>> Jon
>> 
>>      From: Douglas Suhr via Personal_Submersibles
>> <personal_submersibles at psubs.org>
>> To: Personal Submersibles General Discussion
>> <personal_submersibles at psubs.org>
>> Sent: Monday, July 30, 2018 1:16 PM
>> Subject: [PSUBS-MAILIST] Mechanical Depth Gauges
>> 
>> All, as you may've been aware, in late 2015 I purchased Snoopy (a
>> K-250) from Alec Smyth. Regrettably I have been quite neglectful of
>> performing much upkeep on the sub, save for keeping the batteries
>> topped off. My schedule is finally allowing me to spend some real time
>> working on the sub and getting to know the specifics of each system.
>> 
>> As you can imagine, I've been bugging Alec with a question here and
>> there, but thought with this topic I should start a discussion here on
>> the list for the benefit of anyone else who might have questions /
>> curiosities about mechanical depth gauges.
>> 
>> Snoopy's depth gauge is nice and large (about 5" in diameter) so it's
>> easy to read. Alec created a nice label for the gauge face which reads
>> from 0 to 300 (in feet) with the last fifty feet being marked in red
>> to indicate 'too deep.'
>> 
>> Problem is, when I looked at the depth gauge the other day, I noticed
>> that the transparent cover plate on the gauge looked to be quite
>> opaque (to the point where I couldn't quite read the numbers or count
>> the hash marks). I assumed that there was some moisture trapped in the
>> gauge, causing the obscuration. I decided to remove the gauge from the
>> sub and open it up to let it dry out.
>> 
>> After removing the gauge from the sub, I unscrewed three small screws
>> around the bezel and popped off the transparent cover plate. It was
>> only then that I realized the opaqueness was not caused by moisture
>> but a distortion in the clear plastic. The distortion (like super fine
>> scratches) appears to be on the outside of the cover, as though it was
>> cleaned by something that started to melt the plastic or was left out
>> in the sun too long. I don't think either of these explanations make
>> sense, but I'm puzzled as to what might have caused it. I might try to
>> buff / polish the plastic, or perhaps just replace it with glass.
>> 
>> I think it's a good idea to stick a dive computer in viewing range of
>> a viewport for a depth reading, but I like the idea of having a
>> mechanical gauge in the sub as well. A couple of questions that come
>> to mind: what is the pressure variation between salt water and fresh
>> water? Also, although I didn't find moisture in the gauge, The label
>> on the face is wrinkled a bit as though it has seen moisture. Although
>> water should never actually reach the gauge, I can see how moisture
>> from the inlet tube could find its way up into the gauge body. Should
>> I be concerned about drying it out somehow after a dive (especially in
>> salt water)? If so, how should I go about it? ~ Doug S.
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