backup computer

[LFMarm]

2 identical computers to ensure same algorithm and screen layout.

 

[Allen-1]

For technical or solo diving, I'd go with two of the same computers, or two with the same algorithms and settings.

I'm not doing technical or solo diving - I'm doing warm water recreational diving with a buddy. For that, I have an air-integrated G3 as my primary. I have a SPG clipped to my left upper ring, and a backup dive computer, (not a G3), on my non-dominant wrist.

If my primary computer fails - I still have at least four critical data points available:
remaining gas
current depth
MOD
Ascent (or descent) rate

If my primary fails - I'm calling the dive, and using the working tools to do a "normal" ascent and safety stop.
Diving recreationally, up to four tanks a day for multiple days, I've not had my more conservative backup DC lock me out or give me issues - other than one mildly irritating known one:
My G3 starts safety stop at 15' and if I dip back down below 20, it stops it and resumes dive.
My backup DC, (Suunto D5), starts safety stop at 20'.

 

[1070man]

One important thing I read once. If one fails, and you’re doing multiple dives, you might be done for the day. If you have a backup then you should be able to finish dives for the day. Like someone else pointed out, if you were on a liveaboard.

 

[andrespp]

It depends on context: OC, CC. OW, solo, big vs small deco.....

 

[Dsix36]

Most of the previous responses are spot on but I would like to add one recommendation that I firmly believe in. It has made my life (by possibly avoiding death on a very bad day) much easier. I dive with 2 identical computers with all settings matched. I do this for the obvious reasons stated above but also to make sure that I have the muscle memory to use the secondary computer properly in the event of a failure. Not all failures are equal and if it happens on a very bad day, then your mental abilities will be impaired due to the stress induced. Having a backup computer that you are 100% comfortable and familiar can make a huge difference in your outcome.

 

[scrane]

I dive a Perdix and a Garmin Descent Mk1. They both use Buhlmann and track very closely. I like the Garmin because it gives me tactile alarms for ascent rate and a Nitrogen loading graph for quick reference.

 

[Wants2divemore]

When on a trip by myself I dive 2 Shearwaters running identical algorithms (Perdix AI, Peregrine) so that if one fails I can still keep diving for the rest of the trip (I've never had either fail yet, however). When diving locally I just use the Perdix AI, as my 2 sons (my dive buddies) are using Peregrines (they each have their own, I use one of theirs for my trips).

 

[Nemrod]

I started using two computers of same or similar type when a few years ago my computer failed at a most inopportune time. Two is one, one is none. Besides, on a multi-day dive trip, diving many times per day, if your computer quits you will probably lose some dives and there is not always a store handy to grab another. The actual cost of each dive when traveling international is far more than the immediate dive fee, all the lodging, air fares, taxes, tips and on and on. Loose a dive or two or a day and the computer is then cheap travel insurance. Currently I have a Peregrine TX (because it has a compass as I do not use AI) and a standard Peregrine for back up.

 

[Scuba fryd]

I dive with 2 identical computers with all settings matched. I do this for the obvious reasons stated above but also to make sure that I have the muscle memory to use the secondary computer properly in the event of a failure. Not all failures are equal and if it happens on a very bad day, then your mental abilities will be impaired due to the stress induced

this is sumthing i strongly belive in too it might be a bit over kill but going from a top of the class computer to a computer that needs to have a backlight to show an imeige is not sumthing i would want to experience on that one day were it realy counts

 

[LFMarm]

One important thing I read once. If one fails, and you’re doing multiple dives, you might be done for the day. If you have a backup then you should be able to finish dives for the day. Like someone else pointed out, if you were on a liveaboard.

If I was rec diving with just one computer and it failed, I would use tables or planning software to know the time/depth limits for NDL and keep diving.