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Re: [PSUBS-MAILIST] depth gauges

What I was after was something that tells me whether I'm going up or down
& how quickly I'm doing it. In murky water away from any physical reference
its difficult to gauge; & I imagine in a sub you'd want to know you were descending pretty slowly as you approached the bottom. I think one of the many readout options on the Grainger digital gauge was inches. In the pictures of the dial it showed a decimal point but I'm not sure whether the feet depth reading has a % of feet or not. Whatever it's going to be a vast improvement over my 
divers depth gauge.
Alan
----- Original Message ----- From: "Jon Wallace" <jonw@psubs.org> 
To: <personal_submersibles@psubs.org>
Sent: Monday, March 08, 2010 6:33 AM
Subject: Re: [PSUBS-MAILIST] depth gauges
I think that unless you consistently tempt fate and dive near the operating limits of your sub, even a 5% or 10% accuracy would be acceptable for most "recreational" diving. While accuracy in your gauges is a desirable quality, I think Jim's use of "relative" is appropriate and I don't think I personally would spend hundreds of dollars more to get accuracy better than 1%, which seems to be a "consumer" standard. At 500 feet, a 10% error is going to put you anywhere between 450 and 550 feet. With all the variables that go into building a sub in the first place (welding quality, spherical accuracy, materials), it's probably not a good idea to be diving within 50 feet of your calculated crush depth anyway.
The only problem I have with the circular digital gauges cited thusfar is that they have LCD displays which even if backlit are usually on a short timer. So you'd have to have a small LED or other light source shining on it if you went deep or if your eyes are not quite as good as they were years ago. There's nothing I hate more than continually having to press a small button to light up an LCD so I can see it. I'm still interested in seeing an LED based project started with either a multi-display, or a display you can cycle through, that would provide current depth, rate of descent/ascent, water temp, etc, etc. However, after seeing Cliff's small display in the R-300 with all those functions and more, I have to say that is looking like a good solution as well. And it was certainly easy to see in low-light situations. 

Jon
On Sun, Mar 7, 2010 at 7:17 AM, Jens Laland <laland@artematrix.org <mailto:laland@artematrix.org>> wrote: 

    Jim

    The DWYER (0 to 500 psi digital for 125 bucks) pressure gauge is
    not going
    to give you any better accuracy than my own (modified) 6 inch
    stainless
    steel depth gauge (ref. attached image), as these two gauges are both
    members of the same accuracy class, i.e. +/- 1%.

    A lot of times, the so called "better fine adjustments possible"
    is more
    of an illusion made possible by using a microprocessor's ability
    to simply
    add more digits after a decimal point...

    The gauge's microprocessor uses an ADC to sample discrete values
    that it
    reads off the same gauge's analog sensor - so whatever the fancy LED
    display presents you - it'll never be more accurate than the
    accuracy of
    it's analog sensor.

    To get any higher accuracy from DWYER you'll have to spend at
    least $300
    dollars.

    Best regards,
    Jens Laland






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