Which has a higher rate of failure a SPG or a transmitter?

[beaverdivers]

OK, I have checked with my Head Tech. We have roughly experienced a failure rate of 2 SPG's to 1 transmitter for the last 3 years.

We have worked on a ratio of 5 transmitters to 1 SPG for the 3 years.

These have been UWATEC transmitters and Scubapro SPG's.

We only do about 20 repairs a month, so a sample of about 700 units.

 

[redacted]

OK, I have checked with my Head Tech. We have roughly experienced a failure rate of 2 SPG's to 1 transmitter for the last 3 years.

We have worked on a ratio of 5 transmitters to 1 SPG for the 3 years.

These have been UWATEC transmitters and Scubapro SPG's.

We only do about 20 repairs a month, so a sample of about 700 units.

Just to be clear, what is a failure? To me, a failure of an SPG usually means it gets thrown in the trash. Although I do have some older SP SPGs that let me unscrew the face and replace the sealing face o-ring or the plastic face itself. A leak at the spool just tells me that the tech probably failed to service the spool or that rinsing is being done rather than soaking. Such leaks do not interrupt a dive so I would fix it after the dive and not consider it a failure.

Again, to me, the failure of a transmitter is just a piece of what matters and that is tank gas volume information. If the diver is not getting that information when he needs it, the system has failed and the dive is over. A temporary loss that corrects itself in a reasonable time would not be a failure unless it happens too frequently.

 

[endurodog]

Yes, scuba diving for most of us is a hobby that we do not need to do. BUT once we have decided to do it, there is certain gear that is absolutely required to safely participate. I dive quite safely with an SPG and, sometimes, a simple wrist mounted non-AI computer. My decision to eliminate the AI computer (I did fall for one early on) was made based on my needs and the obvious economics involved.

If you need that wireless AI computer to remain safe, then that is one thing you need to safely participate.

Completely agree on the if you need the wireless AI computer to remain safe then there is an issue.

The discussion of needing something or not for this sport is really a hollow argument at best and my point is it should have never came into the discussion. It was used in a context of belittling a point about the computer discussion instead of giving pro's and cons of having one or having a reasonable discussion on the issue. No one has said they need a AI computer to dive in this thread.

 

[Hatul]

I understand how an AI computer calculated gas requirement to ascend on a standard profile, but could you please educate me on how the SOL has any idea on how much gas it takes to make his swim back (to the anchor line, out of the kelp, etc...)

Well, fortunately awap made the problem easy, because he told us it takes 10 minutes to swim back to the anchor line. So all our diver has to do is make sure he has at least 10 minutes of Remaining Bottom Time left.

If you did not have that information, the RBT tells you how much time you have to find the anchor line. In the event you're having trouble finding the anchor line and the RBT is running out, you can ascend and continue looking for the anchor line as you ascend. As you ascend the RBT will increase buying you more time to find the line. If you still cannot find it you can shoot up a SMB on a line and use that to complete the ascent.

Meanwhile our SPG diver gets no help with knowing what he must do first and how much time he has to find the line. He's relying on past experience and intuition or he's totally preplanned and simulated the dive.

 

[GrumpyOldGuy]

Well, fortunately awap made the problem easy, because he told us it takes 10 minutes to swim back to the anchor line. So all our diver has to do is make sure he has at least 10 minutes of Remaining Bottom Time left.

If you did not have that information, the RBT tells you how much time you have to find the anchor line. In the event you're having trouble finding the anchor line and the RBT is running out, you can ascend and continue looking for the anchor line as you ascend. As you ascend the RBT will increase buying you more time to find the line. If you still cannot find it you can shoot up a SMB on a line and use that to complete the ascent.

Meanwhile our SPG diver gets no help with knowing what he must do first and how much time he has to find the line. He's relying on past experience and intuition or he's totally preplanned and simulated the dive.

So your answer is the SOL has NO idea how much time you need to find the ascent line.

I am not trying to convince anyone that AI is good or bad, I all ready admitted I dive an SPG because I am cheap, not because I am a super diver.

What I am pointing out though is the AI computer gives you supplemental information. It does not give you all the information you need and if someone is so inexperienced that the must rely on the AI RBT calculation to dive, they still have significant safety issues that need to be resolved. If you use one because you like it and can run your dive without, then knock your self out.

 

[Bubbletrubble]

I would be extremely skeptical of any statement made by a dive shop owner/employee which asserts that analog SPGs have a higher failure rate than wireless AI transmitters.
My skepticism is based on the following:

1. Anecdotal evidence can be misleading.
2. In the absence of true failure rates (total number of failures/total number of uses), a fair comparison regarding reliability really can't be made.
3. The dive shop stands to make more profit per unit sold on a wireless AI computer system than an analog SPG + non-AI computer (or analog SPG + analog depth gauge + timing device).

Any dive shop that claims it sells wireless AI computer systems vs. SPGs in a 10:1 ratio must be using highly manipulative sales tactics with its customers. There is a high likelihood that it is providing its customers with inaccurate and/or misleading information regarding the failure rates of the respective pressure-sensing devices. I don't think that's a dive shop I'd want to do business with.

Analog SPGs are relatively inexpensive (compared to electronic AI computers). A spare SPG + HP hose can be easily carried in a save-a-dive kit.
When analog SPGs "break," they are almost always replaced not repaired.
Although hoseless AI computers can make gas checks very convenient during the dive, I have been on a fair number of dives where a diver was cussing at his hoseless AI computer during pre-dive checks because it would not sync up with the transmitter. If I had a hoseless AI computer, I would always carry an analog SPG + HP hose in my save-a-dive kit.

 

[redacted]

... the RBT tells you how much time you have to find the anchor line. In the event you're having trouble finding the anchor line and the RBT is running out, you can ascend and continue looking for the anchor line as you ascend. As you ascend the RBT will increase buying you more time to find the line. If you still cannot find it you can shoot up a SMB on a line and use that to complete the ascent.

Meanwhile our SPG diver gets no help with knowing what he must do first and how much time he has to find the line. He's relying on past experience and intuition or he's totally preplanned and simulated the dive.

From what beaverdiver has described, that is not what RBT tells you. RBT assumes you will continue consuming gas at your current rate and tells you how much time you have with no gas consumption rate changes before you must start an ascent. If searching for the mooring line changes your consumption rate then RBT also changes.

It seems to me that regardless of what instruments you are using to manage your dive, you should always have good idea of where you are, where you are going, and how far away it is; especially once you are on a return course. If you don't know where you are going, knowing how many minutes you have to get there as long as you don't change gas consumption rate dose not seem to be much of a solution to your problem.

The SPG diver needs know his plan (where he is and where he wants to be) and that he still has sufficient gas to continue with that plan. When things go pear shaped and the diver (either diver) realizes he does not have enough gas to follow the plan, then he will need more gas (bailout bottle) and/or a different plan. That may or may not include a DSMB. I'd hate to see someone go OOA trying to deploy a DSMB. Probably better to surface and then inflate if you are concerned with OOA. No real requirement to have simulated the dive. But sufficient planning is fairly basic.

 

[joel smith]

Hello everyone I have a Mares AI Puck Air with 66 dives and 67 hrs. of diving no problems yet , I will soon have a spg also just in case. Then I plan on getting a rist mounted computer with a transmitter . I love technology , continually buy , then start all over again.

 

[Hatul]

From what beaverdiver has described, that is not what RBT tells you. RBT assumes you will continue consuming gas at your current rate and tells you how much time you have with no gas consumption rate changes before you must start an ascent. If searching for the mooring line changes your consumption rate then RBT also changes.

It seems to me that regardless of what instruments you are using to manage your dive, you should always have good idea of where you are, where you are going, and how far away it is; especially once you are on a return course. If you don't know where you are going, knowing how many minutes you have to get there as long as you don't change gas consumption rate dose not seem to be much of a solution to your problem.

The SPG diver needs know his plan (where he is and where he wants to be) and that he still has sufficient gas to continue with that plan. When things go pear shaped and the diver (either diver) realizes he does not have enough gas to follow the plan, then he will need more gas (bailout bottle) and/or a different plan. That may or may not include a DSMB. I'd hate to see someone go OOA trying to deploy a DSMB. Probably better to surface and then inflate if you are concerned with OOA. No real requirement to have simulated the dive. But sufficient planning is fairly basic.

Yes the RBT calculation assumes the SAC does not change. If you start hyperventilating you will see the RBT drop. The RBT just helps you estimate how much time you have and with real-time gas planning. It's not a cure all. Also note that when RBT is low it does not mean you're approaching OOA because it allows for a safe ascent with all the stops and with a final tank reserve.

 

[redacted]

Yes the RBT calculation assumes the SAC does not change. If you start hyperventilating you will see the RBT drop. The RBT just helps you estimate how much time you have and with real-time gas planning. It's not a cure all. Also note that when RBT is low it does not mean you're approaching OOA because it allows for a safe ascent with all the stops and with a final tank reserve.

I'd be very careful with the "I have more cushion than I needed anyway" line of thinking. When you violate your gas plan it is time to adjust. If you think it is OK because you were too conservative to start with, then you are only pretending to be conservative.

Plan your dive and dive your plan.