SPG or not

[Badger7]

Don't be this guy

 

[ImpotentSeaSnake]

Don't be this guy
View attachment 888756

The Transmitter Transformer lol

 

[scubadada]

Hi @ImpotentSeaSnake

I dived a non-AI backup to an AI for many years, works fine.

I had not heard of the Z1. It is said to run Buhlmann. The manual has 3 presets, no custom GFs. I can't tell what GFs correspond to SF0, 1, and 2, looks pretty conservative. What do you run your Teric on, will the Z1 match your Teric?

 

[ImpotentSeaSnake]

Hi @ImpotentSeaSnake

I dived a non-AI backup to an AI for many years, works fine.

I had not heard of the Z1. It is said to run Buhlmann. The manual has 3 presets, no custom GFs. I can't tell what GFs correspond to SF 0, 1, and 2, looks pretty conservative. What do you run your Teric on, will the Z1 match your Teric?

Yes I run the Teric on Bühlmann so I can match it. As a newer diver I’m fairly conservative.

I also picked up a Scubapro G3 only because I got a great deal on it, but I think I’m gonna sell it and just stick with the Z1. Reading from other people‘s experiences, the need to resort to a backup computer for rec diving is pretty infrequent. Just wasn’t sure if I would want to scale into the G3 in the future if I got more advanced with diving, but I think I’m fine with a hosed SPG and back up non-AI wrist computer.

 

[scubadada]

Yes I run the Teric on Bühlmann so I can match it. As a newer diver I’m fairly conservative.

I also picked up a Scubapro G3 only because I got a great deal on it, but I think I’m gonna sell it and just stick with the Z1. Reading from other people‘s experiences, the need to resort to a backup computer for rec diving is pretty infrequent. Just wasn’t sure if I would want to scale into the G3 in the future if I got more advanced with diving, but I think I’m fine with a hosed SPG and back up non-AI wrist computer.

A couple things

Scubapro uses a different transmitter than Shearwater so if you used the G3, you would end up like the photo in post #61

Your Teric only runs Buhlmann and has 3 presets in rec mode (45/95, 40/85, and 35/75) as well as custom GFs. I assume you run one of the presets, perhaps the default 40/85 which is moderate in the conservative to liberal spectrum. Your Scubapro Z1 is said to run Buhlmann also but I am not sure if that is straight Buhlmann or a proprietary version. Scubapro is somewhat infamous for their personal tweaks. Your Z1 has 3 presets (SF0, SF1, and SF2) and no custom setting. There is no mention of the GF settings for these. Based on the Z1 values in the owner's manual, it looks like these are Scubapro proprietary settings. These values are only for a 1st clean dive, no idea how the Z1 handles repetitive dives vs. Shearwater. So, it looks like you will not be able to match your Shearwater perfectly with your Z1. In general, you would want your backup to be the same or a bit more liberal than your primary so that it does not go into deco before your primary. Only diving both computers will tell you how close they will run. It looks like SF1 (or SF0) would be a fine backup for a GF high of 85. The Z1 would probably not be the best backup for a GF high of 95 but you could try using SF0.

I dive 2 computers that are not exactly the same, an Oceanic running DSAT and a Shearwater Teric running 80/95. I do not find it a problem. For a no stop dive, I use the more conservative of the two. For light deco, I clear one or both computers.

Good luck in your diving

 

[Belzelbub]

Does this seem like a decent set up or does my backup computer really need AI?

Nope. My backup doesn’t have AI. I’m not familiar with the Z1, so not sure what algorithm it runs. If it’s more conservative than the Teric, you’ll want to make sure you keep it happy during the dive. Easy enough to do, just check both during the dive.

Oh, and I should add. Wearing the different computers on different arms can be beneficial. In my diving, I’ve always got one hand occupied, so looking at the other wrist is helpful. This became real apparent during a rescue course. Helping another diver to the surface will result in at least one hand occupied, so being able to monitor ascent rate on the other is helpful. My backup is a Garmin, which runs the same algorithm and GF settings as my Shearwater.

 

[ImpotentSeaSnake]

“ In general, you would want your backup to be the same or a bit more liberal than your primary so that it does not go into deco before your primary”

Your entire response was super helpful and I wanted to sincerely thank you for that. In regard to the statement above, is the reasoning that you want to be heeding your primary computer while not having your back up nagging you the whole time, but in the event, your primary fails, you still are kept safe from DCS, by your back up?

 

[scubadada]

Your entire response was super helpful and I wanted to sincerely thank you for that. In regard to the statement above, is the reasoning that you want to be heeding your primary computer while not having your back up nagging you the whole time, but in the event, your primary fails, you still are kept safe from DCS, by your back up?

In general, yes. For a no stop dive, the more conservative computer controls the dive. If you have chosen your primary computer to follow its NDL, it should control the dive. You don't want your backup going into deco should you need to use it because the primary has failed. The easiest thing to do is to have 2 computers running exactly the same algorithm.

 

[AsherN]

I've never heard of anyone running out of gas because of an AI computer.

I have heard people running out of gas because the needle got stuck on an SPG at some point and at the time they thought they could continue the dive when they should have been heading up.

AI fails in one way. It no longer gives you a pressure to make a decision.

My Teric and an Icon before that has momentarily not displayed the gas. I keep my eye on it and within seconds it pops back up. That is rare.

To each his own, but anecdotally I've got over 500 dives on AI alone and have never needed an SPG.

If you look at your SPG every so often, you will notice a failed SPG. I look at mine every 10-15 minutes. If I look at it and it shows 2500PSI and I look at it 10 minutes later and it still shows 2500PSI, I abort the dive because the SPG has failed. You also should be aware of your average gas consumption. Assuming the SPG fails in not displaying the correct pressure, I know that if I look at it 45 minutes in a 20m dive and it's not showing between 1000-1500PSI, something is wrong.