Analog Depth Gauge Accuracy

[Rick Vigil]

Thanks for all the replies and suggestions.

I do have another (minor) reason for wanting an analog depth gauge. For many years back in the 80's and 90's I did lots of dives using an analog US Divers depth gauge with a built in bottom timer, plus tables. My depth gauge was in a console with my SPG and it became very natural for me to have my dive plan in my head and simply glance at my analog SPG and analog depth gauge and instantly 'see' where I was in the plan. I'm a visual learner and the analog dials were just so easy to understand. Even after many years of using a digital dive computer, I don't have quite the same quick understanding of my situation, it's as if I need to read the digital numbers and then have do the math of what percentage of my planned depth I'm at. Not hard, but for me anyway, the analog displays are just more natural to use. So I like having an analog depth gauge and am willing to spend money on a good one and carry it while diving. Perhaps someday I'll go all digital and air integrated, but for now I like my analog displays (wow I sound like a dinosaur).

So assuming that brands that use the same mechanical guts in their gauges all the same performance, my question boils down to this:

The linear scale ones must have some sort of gearing in them that counteracts the non-linear motion of the mechanism that responds to the non-linear changes in pressure with depth. Does that gearing tend make them more accurate, or less? That's probably a question for some old engineer who used to work in this area before the advent of dive computers, but I'd thought I'd ask anyway.

Thanks,

Rick

 

[tbone1004]

they are going to all be as inaccurate across the board. Personally, I would want the non-linear gauges. Despite depth being linear, pressure isn't, and pressure is what matters. It also gets more accurate when you get shallower which is what you want because if you are +10ft at 100ft depth, it is pretty irrelevant compare to that same depth swing when shallow.

They are all basically made by one or two manufacturers, so find the cheapest one you can and you aren't going to notice a difference. If you want to know your actual depth, look at your computer

 

[ripman3]

And your problem is???

I don't have a problem. But my point was already made.

 

[clownfishsydney]

I doubt I have seen anyone (even people doing 45+ metre dives every weekend) use an analogue depth gauge for at least 15 years. Buy a cheap computer.

 

[Rick Vigil]

Thanks tbone1004, that's good advice. I'll probably get the XS Scuba one because the font is very readable even without my gauge readers, and I can get it at a discount at my local LDS's spring sale coming up.

clownfishsydney: I picked up a new Oceanic BUD on eBay for ~$150USD which I plan to keep clipped in my thigh pocket when I do a 2-dive day in case my primary (an A300 on my wrist) dies on the first dive. In that case I'll move the BUD to a retractor on my shoulder D-ring for the second dive. But for the first dive and single dive days, I'd rather not have the BUD hanging off of me unless I have to. I've been diving for over 30 years, and many of my habits and equipment choices are still hanging in there. At least I got rid of my horse collar BC!

 

[Valeriy_Kulaha]

I'm in the process of upgrading my analog depth gauge and am wondering if some designs are inherently more accurate than others. I understand that many brands are manufactured by a single company but with different face inserts for different brands.

One popular option seems to be the analog depth gauges manufactured by Pelagic (recently acquired by Aqualung) which have a non-linear scale where the needle moves more at shallower depths. It appears that the Aqualung, Oceanic, Sherwood, Genesis, Tusa, and XS Scuba depth gauges are all made by Pelagic. Are these all the same in quality and accuracy, or does Pelagic do more than just change the face insert to differentiate the brands?

Then there are several other options that have a linear scale where the needle moves the same amount independent of depth. Some appear to be made by the same manufacturer but with different branding, like the Zeagle, Highland, and Apeks but others do not, like Cressi, Suunto, Scubapro, and Oceanics' "oil filled" gauge. Are any of these inherently more accurate than the others, or more accurate than the non-linear Pelagic ones?

I also have an old capillary depth gauge from the 70's. Is it's simple design inherently more accurate than the analog needle ones?

On the one hand, I prefer the ones with a non-linear scale as I'm a recreational diver and my main use of the gauge would be to hold a 15 ft safety stop if my dive computer dies and I thumb the dive, and the 15 ft level is much easier to read on those. On the other hand, if the linear scale gauges are more accurate, that would be safer in that my safety stop would be closer to 15 ft.

Thanks ahead of time,

Rick

1. he did answer the question. The digital sensors are going to be more accurate than the analog ones and not that much more expensive with the added benefit of being a backup computer
2. even if he did read the full post, the answer probably would have been the same. You're going to spend $50-$100 on a new analog depth gauge. They're cheap, but not terribly accurate with most only being accurate to +5ft.

Vs.
Used Dive Rite Duo Computer with Green Case
$100, with a DSS bungee mount, user replaceable batteries, does decompression, etc etc. Fits in most consoles, and will actually do backup computer duty for you. Will be accurate to within +1ft. So here you have a more versatile device, and the most accurate gauge.

Now, the capillary gauge is the answer to the title which specifies analog gauge, especially at shallow depths, but it can flood, isn't accurate the deeper you go, and can be hard to read

Сheap depth gauges use a soft plastic tube. It has poor transparency and a large inlet into which all debris enters.
Oris Aquis Depth Gauge owners have no such complaints about their capillary depth gauge.
This is the most accurate and safe depth gauge and this is the only one type of gauges that always displays correctly and they can be used as a reference for testing other type of depths gauges.

 

[NothingClever]

Oris Aquis Depth Gauge

The price for an Oris Aquis makes it seem like overkill when Rick Vigil just wants something for a recreational SS. This would be akin to taking a Lamborghini to Food Lion to get a loaf of Wonderbread.

 

[Valeriy_Kulaha]

1. he did answer the question. The digital sensors are going to be more accurate than the analog ones and not that much more expensive with the added benefit of being a backup computer
2. even if he did read the full post, the answer probably would have been the same. You're going to spend $50-$100 on a new analog depth gauge. They're cheap, but not terribly accurate with most only being accurate to +5ft.

Vs.
Used Dive Rite Duo Computer with Green Case
$100, with a DSS bungee mount, user replaceable batteries, does decompression, etc etc. Fits in most consoles, and will actually do backup computer duty for you. Will be accurate to within +1ft. So here you have a more versatile device, and the most accurate gauge.

Now, the capillary gauge is the answer to the title which specifies analog gauge, especially at shallow depths, but it can flood, isn't accurate the deeper you go, and can be hard to read

The digital sensors are going to be more accurate than the analog ones... IF
1. It is still sealed and dry
2. Its battery is sufficiently charged
3. All chips inside work correctly
Isn't there a lot of different IF?

Correctly shows only the reference device

 

[Valeriy_Kulaha]

The price for an Oris Aquis makes it seem like overkill when Rick Vigil just wants something for a recreational SS. This would be akin to taking a Lamborghini to Food Lion to get a loaf of Wonderbread.

You can go for bread in an old car with bad steering and brakes and never return home.
In this case, an old bike may be a better solution.

 

[bradlw]

So if the OP is asking the wrong questions for the wrong conclusions, we continue the same?

The OP wants the Analog depth gauge to do the following:



The best and appropriate answer for his "quest" is either a backup computer or a digital bottom time not an analog gauge. Per @tbone1004 's answer above, it doesn't make any sense to use Analog depth gauge of any kind at all. To actually to go out and seek to buy an analog gauge in today's market, is a waste of money and effort.
.........

I disagree
any digital device depends on a battery....and on not leaking...and on no EMP blasts in the area...etc....
If memory servers correctly, I've had two different computer fail on me... and I recall at least one dive buddy had a computer flood. I still have the analog depth gauge I bought during my OW class and no reason to think it doesn't work. I can through the puck in a pocket and never have to wonder of the battery has enough life left for the two dives this afternoon. My old digital bottom timer still wakes up but I have no idea how many more dives it has left in it.

And yeah, I don't care if it reads 15ft when I'm really at 18.5ft.....

checking ebay...yeah, a lot are more expensive than I would have expected.... but still....cheaper than a computer