Air Integration

[Manjula Ellepola]

Can the good people of SB shed some light on the wireless pressure transmitters?

My questions are:

1. From what I read they seem to be very low frequency RF devices. Is this correct?
2. Does anyone know what sort of modulation they use to transmit data?
3. Is it unidirectional i.e the pressure transducer will send data periodically or the does the computer request?

Also would appreciate points to other resources on the web regarding this subject.

Thanks Manjula

 

[tbone1004]

1. depends on which brand, there are several different technologies used for AI.
2. depends on the brand
3. depends on the brand, but I believe most all of them are sending data continuously after the pairing occurs.

Sorry for not being helpful, but it depends on which transmitters you want to use and what you're trying to do with it

 

[RayfromTX]

The transmitter is unidirectional. Only the computer is aware of the pairing. The transmitter just sends out data every so often. It seems like about 10 seconds per update. At least that's how the pelagic/oceanic type work.

 

[mnjhuz76]

The transmitter is unidirectional. Only the computer is aware of the pairing.

Whatever the advantage may be, but Mares states for the IconHD:

"With Mares' bidirectional technology, it communicates actively with the tank module for an unprecedented level of safety and user friendliness."
​

Cheers,
Peter

 

[stuartv]

Can the good people of SB shed some light on the wireless pressure transmitters?

My questions are:

1. From what I read they seem to be very low frequency RF devices. Is this correct?
2. Does anyone know what sort of modulation they use to transmit data?
3. Is it unidirectional i.e the pressure transducer will send data periodically or the does the computer request?

Also would appreciate points to other resources on the web regarding this subject.

Thanks Manjula

I think I am correct in saying that, by far, the most common system in use by recreational divers is the one made by PPS (Pelagic Pressure Systems). The PPS transmitter works with computers from Shearwater, Aeris, Oceanic, Hollis, Aqualung, Sherwood, and Tusa (I believe). All the other ones that I know of only work with the brand of computer that matches the brand of the transmitter (e.g. the ScubaPro transmitters only work with ScubaPro computers).

Just an FYI, in case you are looking for a specific system to research.

 

[Manjula Ellepola]

Thank you for the input. I did further digging and came across a patent by PPS, which says that it is a magnetic based low frequency system. Usually induction based systems work very short distances but I guess it should be enough to go from the tank to the arm. How far away can you get wireless pressure ie from the tank to the computer as you keep increasing the distance between them?

As it is a patented system I guess we would need to get a license to even sniff the signal. The option is to connect a hose directly to the device, Not sure how practical this is as there must be a limit to the number of hoses that you can connect to the tank as some carry a back up gauge as well. Would appreciate your thoughts on this as well.

Thanks for your inputs Manjula

 

[RayfromTX]

The limit with my Perdix AI seems to be somewhere between four and 5 feet. Closer to five.

 

[stuartv]

If there is nothing in between the transmitter and my computer (e.g. standing away from it on a boat), the computer receives the AI signal (from my PPS transmitters) from about 6 feet away, or so. Maybe a little further. If I'm in the water, with the tank and transmitter on my back, I CAN position the computer in such a way, with my body between the computer and the transmitter, to cause it to have intermittent signal.

As far patents and licenses, I would think that if you reverse-engineered the protocol, you would not have to license it, but I am no patent attorney.... OTOH, if you want them to share info with you to make it easy, then, yeah, they'll probably want some payment.

If your objective is to have your wrist device be able to display your and your buddies' tank pressures, I would DEFINITELY recommend to NOT bother with a solution that involves adding ANY more hardware (e.g. a hose or other fitting) to the first stage regulator.

However, for that, you MAY have another patent issue to deal with. The Oceanic Atom 3.0 had a Buddy Check feature, which allows the diver to monitor his own pressure and to see his buddy's tank pressure. Oceanic had to remove that Buddy Check feature and re-release their computer as the Atom 3.1, due to a patent infringement lawsuit. So, regardless of AI transmitter tech patents, the "Buddy Check" idea may have a different patent that applies.

 

[Manjula Ellepola]

Thanks guys.
It is not for buddy check. The idea is to transmit the pressure to the boat at regular intervals so that the boat can keep tabs on the divers. The most convenient way would be to sniff the signal however it is complicated due to the protections in place. We will need to seek advice on sniffing

Going back to the hose idea is it worth considering?

 

[RayfromTX]

Thanks guys.
It is not for buddy check. The idea is to transmit the pressure to the boat at regular intervals so that the boat can keep tabs on the divers. The most convenient way would be to sniff the signal however it is complicated due to the protections in place. We will need to seek advice on sniffing

Going back to the hose idea is it worth considering?

Not in my opinion. It seems like going backwards while developing a cutting edge system.