Wireless Tank Pressure Sensing

[BigTuna]

How does in-water communication work between the tank-mounted sensor and dive computer mounted on your wrist? How does it fail? Do you back up your "wireless" system with a conventional SPG?

 

[outlaws]

I use a Suunto Vytek wireless transmitter. I have not had any problems at all. I am a tec diver so I use redundant spg and bottom timer allthough I have never had to go to the back ups.

Butch

 

[Tienuts]

I have an Oceanic VT pro which I have used on over a hundred dives without a problem. I do have a set of analog guages as a back up.

The only times I have lost the link, is when the transmitter battery gets low, or when using a scooter. When running, the scooter motor interferes with the transmitter, and it wont pick up data.

 

[CompuDude]

I have the Uwatec SmarTec. I've lost sync for a second or two before, but nothing I'd consider serious. I recently added a backup SPG, but that was for tech/DIR purposes moreso than feeling I was in danger without it.

When it loses sync, the only thing that happens is the tank pressure changes to "-----" for a moment or two, then it comes right back. Not a problem thus far.

 

[ApexLongimanus]

I never had a problem with UWATEC Aladin Air. Have a small SPG as back-up, though.

 

[stefusa]

If you're doing photography, maybe avoid wireless air integration since the flash induce the loss of transfert between the sensor and the computer.
It's coming back after few sec but if you're flashing like hell.....

my 0.02

 

[jeffrey-c]

I don't think you asked people what they used, but how does the communications link work and what impacts it. The transducers use a low power RF transmitter putting out a low frequency signal in the 35kHz (I think Cochran's use this frequency) to 200kHz range (used by some others). The pressure and battery voltage are converted to digital data and then are modulated onto the RF carrier.

As a transmission medium, water attenuates RF greatly, particularly as the frequency goes up (as seen with a satellite TV signal during a heavy rain). The comm link can basically be described by output power and directionality of the transmit beam, attenuation of the water and other materials, and the "noise" at the receiver. To successfully "close the link" requires a certain level of signal-to-noise ratio. The RF transmitter on the transducer operates at as low of power as possible to extend battery life, so the output powe is limited. Things like your body, wetsuit, etc. all add to the water's attentuation. And things like camera strobes can create more RF noise at the receiver, impacting the comm link. When the comm link signal-to-noise drops below the necessary threshold for robust communications, the link is lost and the system will then try to re-acquire.

Outright failure can be caused in the tank-mounted transmitter by battery voltage dropping below threshold, failure of the pressure transducer, failure of the analog-to-digital converters, failure of the microcontroller, failure of the modulator, or failure of the RF power amplifier. At the receiver end are similar potential failure points.

While I am a technology person, I personally feel that there are too many potential failure mechanisms here and resulting complexity and cost, and hence I do not use wireless pressure for my diving.

 

[29South]

If you're doing photography, maybe avoid wireless air integration since the flash induce the loss of transfert between the sensor and the computer.
It's coming back after few sec but if you're flashing like hell.....

my 0.02

This is certainly a matter of personal preference however, following a strobe flash the link is re-established in the order of 2-5 seconds. Of note is that most systems will not go into alarm state until the link has been lost for 15-30 secs... so a momentary display irregularity is the most you would expect to see...

On the other hand, if you have a scooter, like a prior post indicated you can forget about wireless as scooters are well known to cause link failure.

 

[29South]

Outright failure can be caused in the tank-mounted transmitter by battery voltage dropping below threshold, failure of the pressure transducer, failure of the analog-to-digital converters, failure of the microcontroller, failure of the modulator, or failure of the RF power amplifier. At the receiver end are similar potential failure points.

While I am a technology person, I personally feel that there are too many potential failure mechanisms here and resulting complexity and cost, and hence I do not use wireless pressure for my diving.

The use of wireless is a personal issue. but as for the comments you raise.

1. Cost ? yes, they are pricey...but it is market pricing...the pricing is not driven by the cost of goods sold...It is a desirable feature and the market is willing to pay.

2. Complexity??..hardly... IMHO these systems are trivial in complexity for todays norms of circuit design and the circuitry includes components with MTBF data reaching 100k's hours so raising the potential failure mechanisms is simply FUD spread. Note there is nothing radical, revolutionary or fundamentally new in the applied technology in the wireless scheme.

To reply to BigTuna's original question, personally I do not carry a backup to my VT3. As a rec diver, unlike tec, there is no safety issue other than a called dive resulting from a damaged or faulty transducer (be it wireless or SPG)...



If i was tec diving i would have backups for pressure gauge and for computer, regardless whether my primary was wireless or not.

oh..and it looks cool

 

[CompuDude]

If you're doing photography, maybe avoid wireless air integration since the flash induce the loss of transfert between the sensor and the computer.
It's coming back after few sec but if you're flashing like hell.....

my 0.02

Depends on your setup. My Inon D2000 strobe doesn't seem to affect my Uwatec wireless AI rig in the slightest.