SPG with integrated transmitter. Am I the only one who would like that ?

[2airishuman]

What I did not see pop up again, is some suggestion I made then, during the fray : how about "upgrading" the classic analog SPG with a passive transducer+radio, such as those chips used in truck tyres nowadays, so that there would be no more need for separate transmitters, with all their o-rings, 'fake-handle' lumps, discharged battery problems, etc ... The transmitter would respond realtime to the dive computer queries, not at a fixed sample rate, and would be passive like a beacon or harvesting the radio energy from the dive computer.

These are two separate technological questions, so let's break it down.

1) Does it make sense to integrate the AI transmitter into the analog SPG?
2) Can the AI transmitter be passively powered?

They're separate.

Regarding integration, technologically, yes, you can do it as part of one mechanism. It would involve a lot of engineering, but it could be done. One question would be how much larger the SPG housing would be. I would imagine it could be kept fairly small. The problem here is that the number of divers who want an analog SPG combined with wireless AI is small so it's a tiny market and therefore hard to recover engineering costs.

Passive power depends on larger antenna sizes, shorter distances, and more power from the active device (the computer, in this case). I don't think it works for this application.

 

[Aqua-Andy]

What problem are you trying to fix? I go by the age old saying "if it ain't broke then don't fix it", my SPG on a hose works just fine. Why do we need to overcomplicate things? Take braided hoses for instance they were supposed to be the cure for all sorts of hose issues, that did not turn out so well. I think I'll stick with what I have, it works and is stupid simple.

 

[fnog]

The problem is that breathing water hurts a bit. You got a stupid fix for that ? Me too: not go underwater. It is a fix that is stupid simple and works great.

OK. Jokes aside, now that I realized that a passive transmitter is unlikely, I wonder about the opposite. The tank contains a tremendous amount of energy with compressed gas. If an electric generator integrated inside the first stage would run by dropping pressure to,say, 80bar, there would be energy available throughout the dive to recharge a supercapacitor in the transmitter. There would even be some available to radio-recharge devices in very close proximity. No good for video lights, but it could save a flinching computer. Then again, that is probably too much change in a too-critical piece, the first stage. In view of the benefit.

 

[tbone1004]

if you run at 80 bar then it won't work well below that pressure plus some sort of margin to in the first stage, so call it 1500psi to work with, so that's out. You also need a gas outlet because in order for it to spin the gas has to go somewhere so when you turn it on, to generate power you need to burn gas. People aren't going to want to do that unless you can get it to bleed the same or less gas than the sherwood first stages, but I don't you'd be able to power anything from that.....

 

[stuartv]

The tank contains a tremendous amount of energy with compressed gas. If an electric generator integrated inside the first stage would run by dropping pressure to,say, 80bar, there would be energy available throughout the dive to recharge a supercapacitor in the transmitter. There would even be some available to radio-recharge devices in very close proximity. No good for video lights, but it could save a flinching computer. Then again, that is probably too much change in a too-critical piece, the first stage. In view of the benefit.

What is the point? To make the transmitter smaller than the ones that are currently on the market?

How about one of these ideas:

- improve the battery tech and put a smaller capacity battery in. My Atom transmitter has the original battery still in it, after 21 months and over 100 dives. And the transmitter battery status still shows as Good on my Atom. I don't need the battery to last nearly that long. So, how about a much smaller battery that has to be changed more often? This would go along well with any improvement that could be made to the pressure transducer and radio transmitter sizes, too. If a transmitter were 1/4 the size of the current ones, that would be nice.

- standardize and commodotize the transmitters. Get the industry to establish a spec so that different brand computers and transmitters could work with each other. Then reduce the transmitter size and cost - in the way that only mass adoption of a standard can foster. Make it small, seal a coin-sized battery inside, so that the transmitter becomes disposable but will last a year of normal use, and make it cheap.

Now that I think of it, it seems like if one of the computer OEMs would publish their transmitter spec and open it up for others to use the same spec, they would have a serious shot at dominating the market. A lot of the others would resist using someone else's spec - at least at first. But, if it were done right, I could see everyone eventually being dragged to the table to support a common hoseless AI standard. Especially if it were someone like PPS, that makes computers for a bunch of different brands.

Once the spec is "open", then the door is open for someone to innovate and produce a transmitter like I described above (i.e. very small and cheap - maybe with a sealed battery and disposable or maybe not). And once someone produces a reliable, cheap transmitter that works on an open standard, I think a lot of the people who want AI would drive the market to supporting that AI standard. I would certainly prefer to buy an AI transmitter that could work with many of today's computers and at least had the potential to work with other computers, even of different brands, in the future.

 

[fnog]

if you run at 80 bar then it won't work well below that pressure plus some sort of margin to in the first stage, so call it 1500psi to work with, so that's out. You also need a gas outlet because in order for it to spin the gas has to go somewhere so when you turn it on, to generate power you need to burn gas. People aren't going to want to do that unless you can get it to bleed the same or less gas than the sherwood first stages, but I don't you'd be able to power anything from that.....

A supercapacitor has an energy density that is a good order of magnitude less than lithium ion batteries, but it is still plenty to complete the dive after you are below 80bar. Those have the advantage over Li-ion of not ageing and being charged with any current thrown at them. Assuming it is completely discharged to start with, your surface check breaths on primary and backup regs would be enough. Because that is where the gas goes: in your lungs.

Now, with 100% O2, one probably does not like having a small power plant inside the first stage. So that idea is no good for stages and rebreathers. Just don't take my musings too seriously. That is all blue-sky stuff.

Stuart, you are right. A great step forward would be de-facto standardization and commoditization. Let us just hope this happens soon, so that all scuba brands reduce their non recurring costs and bring life to the PDC developments, or else we could go on forever with those units that look like a trip to the eighties or a charcoal iron, sold for the price of 2 iphones.

 

[Aqua-Andy]

Make it small, seal a coin-sized battery inside, so that the transmitter becomes disposable but will last a year of normal use, and make it cheap.

If this ever comes to fruition it should be fun trying to get this thing apart to replace the battery. You know that someone on SB will figure a way to change the battery and post it here

 

[Lorenzoid]

I recall the original discussion in which this hybrid was proposed. Sure, it sounds great. But even assuming the technical challenges can be overcome, and it can be sold for an attractive price, it's likely to be a specialty item, produced by one manufacturer. I like the fact that if my generic mechanical SPG breaks, I can readily purchase the exact same thing at almost any dive shop to replace it. I have a strong preference for generic gear over specialty gear whenever feasible.

 

[tbone1004]

A supercapacitor has an energy density that is a good order of magnitude less than lithium ion batteries, but it is still plenty to complete the dive after you are below 80bar. Those have the advantage over Li-ion of not ageing and being charged with any current thrown at them. Assuming it is completely discharged to start with, your surface check breaths on primary and backup regs would be enough. Because that is where the gas goes: in your lungs.

Now, with 100% O2, one probably does not like having a small power plant inside the first stage. So that idea is no good for stages and rebreathers. Just don't take my musings too seriously. That is all blue-sky stuff.

Stuart, you are right. A great step forward would be de-facto standardization and commoditization. Let us just hope this happens soon, so that all scuba brands reduce their non recurring costs and bring life to the PDC developments, or else we could go on forever with those units that look like a trip to the eighties or a charcoal iron, sold for the price of 2 iphones.

not at 80 bar it isn't going into my lungs.... It's coming in at 10 bar over ambient, so you have to design it to run off of the changing IP with depth

 

[Charles2]

@fnog It's thoughts like yours that stimulate innovation in diving. Kuddos!

One thing that I might suggest is that the SPG be digital instead of analog. It could still be located at the end of a hose and clipped to your harness so that you could read it at any time. In addition, it would be independent of the dive computer and it could easily contain a transmitter capable of communicating with any manufacturer who decides that this has merit (read profit).

I suspect that such a device will be more expensive than a standard analog SPG, but it does sound sexy. It will still come down to personal preference. There will still be many who do not trust an electronic gauge with either a digital or an analog readout. The same discussions went on in the skydiving community well over a decade ago. Today it is very common to see digital altimeters on many skydivers. Most consider the digital devices to be more accurate. In addition, most digital altimeters contain a downloadable memory that can reveal exit altitudes, opening altitudes, fall rate, etc. The mind boggles at the possibilities.

Thanks for the stimulating post!