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
************************************************************************ ************************************************************************ ************************************************************************ The personal submersibles mailing list complies with the US Federal CAN-SPAM Act of 2003. Your email address appears in our database because either you, or someone you know, requested you receive messages from our organization. If you want to be removed from this mailing list simply click on the link below or send a blank email message to: removeme-personal_submersibles@psubs.org Removal of your email address from this mailing list occurs by an automated process and should be complete within five minutes of our server receiving your request. PSUBS.ORG PO Box 53 Weare, NH 03281 603-529-1100 ************************************************************************ ************************************************************************ ************************************************************************