analog vs digital gauge (SPG vs Air Integrated Dive Computer)

[AJ]

Do diver typically use 2 dive com for redundancy, or 1 dive com 1 dive console, or just a dive com alone?

I dive with 1 SPG and 1 computer, no AI. I know by guestimate quite exactly what my air reserve is at all times. I do check air every 5 to 10 minutes if my guestimate is not too far from reality and keep an close eye on NDL and depth at all times to make sure they are within limits. If the computer or the SPG would fail, it means end of dive immediately, no questions asked. I know I will make it back to the surface safe because I know I have plenty of air left and I know my depth I am departing from, even without my SPG or computer. With ratio deco and the help of my buddy failing instruments to me are a nuisance, not an emergency situation.

The real question (I know, can of worms ) is: how much do you (want to) rely on your instruments to dive safely? If you need an alarm to tell you you're running out of air, the problem is not a failing SPG or computer :blinking:

On topic: buy what you like. I you like number crunching, go for AI. If you want to be a wannabee techie with SPG, go for it. But train yourself to be always aware of air consumption and bail out plan. That's what really matters, not the tool.

 

[snsb]

Hi again, tbone1004

I will rethink the idea of console but either way redundancy seems like a way to go, so may be I should spend more time researching dive com as well.

Regarding the price, I don't really understand the price variation and brand position of dive com yet.

Suunto that you said they are overpriced, they also have cheaper model. Is it inferior product compares to more expensive version (Eon steel)? (Cause from what I understand, most of the features seems to involve in software rather than hardware)

What about higher end product such as H3 or Petrel2 that you mentioned, is it much better and also considered good value for money?

Most of these brands I will have to order online as I cannot find them locally, if that is the case, do you know anything about Liquivision as that and Seabear is the two high end brand that looks promising in my opinion.

Thank you

---------- Post added December 7th, 2015 at 11:43 PM ----------

Hi AJ

Thank for the tips

I am quite new to diving but I considered myself to be a very conscious diver and check my instrument quite often.

However, I will be focus on photography most of the time, and even though I check the gauge regularly, I might actually forgot the remaining air that I checked last time and in this case, SPG with stuck needle will be very scary.

Thus, this is why I create this thread in the first place.

But after reading this thread, I guess redundancy is the way to go, regardless of digital or analog. (But I guess relying on instruments will also helps hehe)

Thank you

 

[tbone1004]

best bang for the buck is the Petrel 2. No real need for redundancy at your level of diving, that and an SPG is about all many cave/tech divers will take for light tech diving and certainly all most of us take on recreational dives. Our DSMB reel will have knots every 10 feet for gauging ascent rates and safety stop depth, but for NDL diving you can also use your buddies gauges as backup. Same rationale for why you don't dive with redundant gas supplies.

Eon Steel is stupid, don't buy it. Hideously expensive, hideous, and still uses Suunto's proprietary algorithm. The Zoop is a waste of money because if you even think about any sort of technical diving it becomes a paper weight since it is single gas, no decompression, and doesn't have gauge mode. It's bad. You also have no control over how conservative your NDL's are because of the fixed algorithm. It's annoying.

The big manufacturers also passed around a bunch of stuff this year, so Aqualung bought PPS from Oceanic, dropped Suunto which has now gone to Huish who owns Zeagle and Atomic, and Seabear sold out and is now owned by Scubapro which is the reason for the delay in AI transmitters for the H3.

http://www.scubaboard.com/forums/co...564-need-help-choosing-new-computer-read.html
Read this thread as I went through quite a few options, obviously using USD and some things have changed with the company transitions the last few months. The only real change is that for an intro level computer, the new option from Deep6 which will be available in a few months has comparable features to the Geo 2.0, but instead of $400, is $140 usd, so the options really boil down to that at $140, the Geo 2.0 at $400 if you need a watch instead of a puck form factor, then straight up to the Petrel at $750, or if you really need a fancy watch, the Seabear H3 at $900. The only exception is if you work for a dive shop and have to be bound to a certain brand of gear, but that is certainly the minority. If you weigh all of the cost vs quality vs features etc there really is no other computer on the market that is worth bothering with. All of the "tech" computers come too close to the price of the Petrel or exceed it and the only feature it doesn't have is a smaller form factor, where you go to the H3, or it lacks AI, which as you can see from a simple recreational dive profile above, you don't actually need, and it becomes a hindrance for technical dives because of the need for multiple transmitters with analog redundancy in case of a transmission failure, which now limits your regulator selection because you have to ensure it has 2 HP ports etc etc.

 

[halocline]

I will rethink the idea of console but either way redundancy seems like a way to go, so may be I should spend more time researching dive com as well.

I would not be so worried about redundancy. You are diving in OW, no decompression, with a buddy, correct? You don't need a back up way to check gas pressure. First, SPGs are very reliable and almost never "quit working" on a dive. Probably the most common failure is one of the spool o-rings gets blown out and they start leaking. This almost exclusively happens when first pressurizing, before you get in the water, rarely during a dive. Second, with a little experience you will get pretty good at estimating your remaining air, and since you are ALWAYS diving in a way that gives you access to the surface and a buddy, if your SPG does fail during a dive, you'll have some indication of your remaining air and can proceed calmly to the surface with your buddy. IOW, if you are diving smart, you will never have to worry about running out of air, even if your SPG suddenly quits.

Likewise you do not need redundancy for depth information, again, because you are diving OW, NDL, with a buddy. If your computer or depth gauge suddenly failed, you can simply use your buddy's depth info to make an orderly ascent, complete with stop if you want. I normally do carry a back up timing device, just a regular dive watch with a bezel. That's more out of convenience than any other reason; I just don't want to take my watch off to dive, and it's very easy to just glance at my watch to get an idea of elapsed dive time.

Dive safety is all about judgement and decision making, not so much about extra gear. Spending some time learning about basic decompression theory (there's a good chapter in the PADI encyclopedia) and getting a sense of the factors in DCS incidence can result in more intelligent dive behavior, which is a far more effective safety approach than wearing an extra computer.

 

[DA Aquamaster]

Hi DA Aquamaster

Thanks for the history lesson that is very insightful!


Regarding the battery in electronic SPG, I fully understand what you said but a little confused about the voltage drop.

Do you think the case of failure is due the lithium ion in electronic SPG (or badly design enclosure) and not just any battery in general? Otherwise wouldn't other electronic device such as dive come suffers from the same failure?

If so, I will then have to think twice about using any device with similar battery inside.?

The batteries in question were your basic 2032 button cell batteries and for what ever reason once they had some hours on them, when they got cold the voltage would drop enough that the unit wouldn't function.

I've never had issues with a dive computer, etc using a larger battery like the Saft LS 14500 litihum batteries. I think that's an artifact of both having large capacity combined with setting the low voltage warning high enough that you really can get another dive out of the battery even in cold water.

Regarding the 5)c) "SPG that reads high at the low end of the scale will have a needle that won't go all the way to the zero stop"

Does it get worse over time or something that can happen instantaneously? Is there anything we can do to prevent this?

There are two issues in play here.

The first is just calibration error. SPGs operate off of a bourdon tube that is curved or C shaped and in essence straightens when the inside of it is pressurized. That movement is what operated the needle. The mechanism is calibrated at a specific pressure (usually somewhere in the middle) but the tube may not have perfect linearity so it may be off a bit at one extreme, or the other, or both.

The other problem is due to dropping the gauge and that depends to a great extent on how the SPG is made. If the needle is just pressed on the stem, the momentum of mechanism when it impacts the ground can twist the stem inside the needle's socket. With the needle held against the pin any twisting of the stem isn't noticeable, but the actual 'zero' position may be below the zero stop pin.

In contrast if the stem twists the other way, the needle now points above zero and the diver knows there is something wrong.

Prevention comes down to not dropping your SPG or letting it swing like a pendulum into a hard object.

 

[CuzzA]

Hi CuzzA

It really helps. Your technique sounds like a good way to go.

Depth and Pressure monitored by analog and digital device and redundancy in both areas too.

Regarding the wireless AI is there any downside to it? I remembered reading that wireless AI works well in most situation excepts behind scooter, as its magnetic will interfere with the link. That's about the only downside I know.

Also, any brand/model is appreciated

Thank you

Sure. During my research on computers I narrowed down my options to 3 computers. All of which I believe are very good computers.

DiveRite Nitek Q ($400), Shearwater Petrel ($750) and Mares Icon HD ($500). I ended up purchasing the Mares Icon new on sale for $700 including the wireless transmitter ($200).

I'll break down why I made that decision in a few categories with some pros and cons. Note, there may be some other good options, but these three were the ones I settled on comparing.

Display: The Icon display is better than the other two. I can glance at the computer and immediately process all important dive data without having to think about it. The color coding really helps to distinguish what's what. I found the Nitekq to be the worse of the three with the very blah yellow display. It reminded me of an old DOS computer display. The Petrel display is nice, but still doesn't compare to the Icon.

AI: Neither the Petrel and Nitekq are air integrated computers. That was probably the biggest reason for not choosing one of them. It doesn't make them a bad computer, but for me personally I really like the AI. I like that I can look at one source and know exactly what my status is during the dive. This is especially useful for hunting and photography as you are already task loaded with that activity. I also felt as a new diver the AI would be beneficial to me as a redundancy with my SPG. There's a lot to process for a new diver and I liked some of the safety net features the AI provides. To answer your question about AI and scooters, I do not know if a scooter would effect AI as I have not used a scooter yet.

Gas Type/Switching: Clearly the Nitekq is the leader when it comes to Gas Switching. You can program 7 different mixes. Both the Petrel and Icon allow for 3 gases. In terms of gas type, the Petrel and Nitekq beat the Icon since the Icon is not a Trimix computer. This is a non issue if you don't intend on diving trimix. I hope Mares will add Trimix capability with a future firmware update. I should also note the Nitekq and Petrel support closed circuit rebreathers while the Icon does not. Again this is a non issue if you never decide to use CCR's.

Features: The Icon has a couple distinct features the other two do not. One is the ability to store images. Some may question whether this is a worthwhile feature and IMO, it is. Here's an example, on a recent spearfishing trip the feature came in very handy. When we were coming in we were stopped by FWC. Naturally they asked for everyone's drivers and fishing license. Everyone on the boat was scrambling to find there wallets, meanwhile I just pulled it up on my computer and presented my licenses (I did not nor needed to bring my wallet). I also store my health insurance card, DAN card, and a credit card on the computer. Second is the ability to store maps. Especially wreck maps that can be pulled up during a dive. If you take a wreck dive course you will learn to draw a map survey of the wreck on a slate or wet notes. This is good, but doesn't compare to having a digitally produced map with all important data about the wreck.

Connectivity: The Icon and Nitekq includes a USB connector which also serves as the battery charger. The Petrel uses included Bluetooth. This didn't impact my decision.

Battery: I give a slight advantage to the Nitekq and Petrel since they have user replaceable batteries whereas the Icon has a rechargeable battery that must be factory replaced at around 500 charge cycles. The Nitekq battery is also rechargable and is supposed to last approximately 300 charge cycles.

In summary these were the major things I considered. Again this is my opinion and some may disagree with my reasoning. There also may be other computers that are worth considering. At the end of the day though and again in my opinion, if Mares adds Trimix to the Icon, it will be the perfect computer. I'd also like to see a brass and chrome transmitter.

One final point. Since Mares has other computers I can add a backup computer like the Mares Puck for example and both will be running the same algorithm and theoretically should calculate my dive the same. And since I can buy one for ~$150, that's a pretty inexpensive backup. I'll also note for the sake of this conversation I purchased the DiveRite brass and glass SPG.

Again, I hope this helps. I knows it's a long post, but I'm home sick and lost my voice at the Bucs vs Falcons game yesterday so I've got nothing better to do.

 

[dmaziuk]

May I ask why wired AI computers would be inferior to wrist dive com? I thought it use similar electronics and algorithm inside?

I think the basic problem is that vendors with the best feature sets: Petrel, OSTC are not interested in adding wireless air sensors because their main target is rebreather and tech divers who use WAI rarely or not at all. The ones with the WAI grew out of "recreational" computer and are nowhere near as good in terms of features. Electronics and algorithms may be similar to some extent but the amount of customization, ease of use, screen quality and so on and so forth are very different.

 

[Hatul]

I'm a big believer in AI ,being a recreational diver, because it's easier to glance at your wrist and see your pressure each time you look at your computer. We know that biggest cause of dive accidents is low or out of gas and failure to glance at your SPG. Also you get real time guidance with the air time calculations.

Having said that my personal experience also has been that the analog SPG is more reliable than my wireless transmitter. In fact in my last trip to Cozumel my transmitter flooded, and disconcertingly before it cut out it was coming on intermittently and showing a pressure about 1000 psi higher than my SPG. For this reason I highly recommend having an analog SPG as a backup to the transmitter. Because I had an SPG I continued my diving as I backed down to what most others were using without AI.

 

[tbone1004]

CuzzA, this is not to downplay your decision, just analysis.

The petrel display is every bit as good as the icon btw, it's just different. If you look at the Shearwater Recreational Nitrox mode it displays comparable information that is easier for most divers to process. The info on the Petrel tec screens is crucial to see easily for a lot of technical divers and most of us just leave it there, but the recreational mode puts the same info right in front of you. What is interesting with the Q is it actually has a VERY nice screen, it's just programmed poorly to optimize battery life which is why it isn't multi color and super high frame rate.

AI being used like that is an equipment solution to a skills problem. In this situation it is likely not your fault, but your instructors fault for improperly training you. It's the system, it sucks, but it is what it is. While seeing all the info on one screen is nice, that is about the only justification for AI. The redundancy is not needed at this level, nor is it used in any kind of technical diving where analog SPG is the primary.

Gas switching. The petrel allows for 3 gasses in recreational mode, but 5 in other modes which is all you really need. 7 is more than most divers will be using because you'll be on CCR. I have yet to see a dive profile that actually utilized more than 5 gasses. The WKPP has 7 total gasses, where you would only ever carry up to 6, one of which is a 16/45 deco mix for back gas breaks. A 300ft dive for me on OC would be 12/70 backgas, 21/35 35/25 50/50 and 100% deco gasses for a total of 5. Using the 35/25 as a travel gas to 120ft.

Picture feature I will yield is nice, however the amazonbasics thermal laminator works pretty darn good to put stuff in wetnotes that are carried. I would say this is nice to have, but certainly not a selling point.

Battery-nitek is not user replaceable. It is internal charging only. Petrel really trumps here because it can use any AA format battery which is super nice when travelling. Throw an extra AA in a ziploc baggie with a nickel to open the compartment and you're good to go vs having to remember the usb cable. The Nitek at least uses a standard USB cable that is available anywhere, but while the Icon likes to say it uses a standard USB cable, you still need the clip and if you lose or break it, you are not in a good position.


@dmaziuk. Seabear designed the H3 and T1 around the use of wireless AI. The computers have the hardware in them already. Scubapro has to finalize the development of the transmitters and they will be a true tech computer with the ability for wireless AI. Unfortunately because AI is seen as a gimmick to most of the tech mfg's markets, Shearwater has been very vocal about the fact that they have no intention of developing AI *though wired is available in a couple of Divecan powered rebreathers, but it won't be wireless, too expensive to justify*, and they really shouldn't until a big leap is made in the technology to allow the transmitters to work. They're too expensive, big and bulky right now for any tech divers to be interested in them even if they were deemed reliable

@Hatul, you just perfectly described an equipment solution to a skills problem. If you do not know how to properly plan your dives to where you are not surprised that you are out of air, then you are not adequately prepared for that dive and you are using the transmitters as a crutch to improper dive planning and situational awareness. You being general, not specifically directed at you personally. It's a sad state, but if you can't trust yourself to be situationally aware about your gas supply, then you need to fix that quickly because all of the beeping, vibrating, and whatever other alarms the recreational computers use to get your attention when you screwed up can fix a true OOA situation if you become complacent and start ignoring them.

Think of this like the fuel gauge in your car. Your SPG is like the needle on the dash, there if you need to look at it, but you only pay attention to it every once in a while because it is not something you need to know all of the time. Your speed, and awareness to what is around you is much more important. Wireless AI is like the digital gauge that tells you how many miles you have left on the tank. You don't trust it completely, but it is pretty accurate. Do you really need to know how many miles you have until empty every time you look at the dash or do you just need to know approximately where you are on the whole tank? I know I can go about 300 miles on my gas tank, and I can very quickly look down and see I'm around a quarter tank so it is time to fill up. Takes a lot more thought to process a specific number of 75 miles DTE. No one needs to know their pressure with better than +_100psi accuracy. It's just not necessary.

 

[CuzzA]

Thanks for the added info about the technical use of those computers. That is beyond my level of diving right now, but certainly is something to consider for a diver who knows they are going to be entering technical diving in the near future.

I understand your point about a solution to a skills problem. Personally, I do not think this applies to me at all. I'm very aware of my situation during a dive. I constantly check my gas, probably more than necessary and having that data on my wrist makes it simpler. Especially if I'm shooting fish, stringing fish and looking for my next target. I can simultaneously see my gas supply while doing all three of those activities. An SPG alone would require I stop all activity and unclip my SPG to view it. Nothing wrong with that, but I feel like I have a solid understanding of my gas consumption during a dive. I would never rely solely on an alarm to inform me about my gas. Like I said, I use the alarm to cross check the SPG and AI are in agreement. The other nice thing about the gas alarm is it forces you to make a simple gas plan even for a simple dive. I set my turn pressure and ascent pressure. By doing this I know what that number is in my head because I made the plan predive and based on depth. Rather than some people who really don't think about it and just plan to ascend once they hit X amount of pressure.