23 Comments on “Should I Get A Dive Computer With Transmitters – 8 min”

  1. Hi Steve and Vas this was interesting to listen to, I have the capability on my computer I just haven’t bought the transmitters.

    My main interest in them is seeing how my SAC rate is affected throughout dives without having to do a sac test which in itself is a little articifical. What are your thoughts on that? Useful or knowledge we’ll develop over time anyway? I particularly worry about getting lazy as Vas mentioned, if my computer tells me my sac why would I calculate etc which i find a good thing to do from a skills practise pov

  2. Vas Proud

    Hey Chris,

    Good to see you are still watching 🙂

    I think that anything that can help you plan a dive or feel good during the dive has to be a good thing.

    The question (for me) is whether the computer is the best or only way to do this. If you take the data from a dive and get yourself a SAC rate to act as a baseline (you know the average depth from the computer and the gas used from your ending pressure etc. – we cover that in a video actually). Now, when you plan a dive, you know some of the key depths of the dive – so you can know upfront what the gas you are using per minute would be for that depth. So as you progress along that level, you would be able to see if you are using more or less gas than anticipated.

    Of course you will vary the breathing rate during the dive based on factors like comfort level, exertion level and say getting cold – so I am not sure it makes too much sense to try to dig too deep and get to a minute by minute level of accuracy.

    Instead, if you think about the safety of using a gas rule like thirds or fourths, you will generate a turn pressure or “minimum gas” needed when you start your ascent. So you have a hard limit you can’t go over and you will also know when that should come (after how long) – so what I like (and I think we maybe spoke about) was having a “way point” at say half way through the bottom phase of a dive – so we know the gas we would have at this point as well as the gas to start the ascent. We can therefore see if we are ontrack or if we are likely to have to start an ascent earlier.

    So knowing the “live” SAC is not helpful to me – especially as gauges read BAR/PSI and not Litres, what is helpful is knowing when I am going to get to a key gas way point so it doesn’t catch me out.

    What is really useful to me is to generate a table for the typical tanks you use (say 2 x 12L) and take your SAC rate and turn that into “BARS every 5 minutes” for the main depths you will be at (10, 15, 20, 25, 30, 35 etc) and then add columns for higher and lower SAC rates. Now you know that every 5 minutes that passes at 20m, you will have used “x” Bar – so this is what tells you how you are doing. What then happens is that you will “see” your SAC rate based on data you collect on the dives and will need to look at the SPGs less and less. You will also start to tune into how your breathing feels to you and use this as a cue as well – I can tell long before I look at my gauges if I am feeling super relaxed and therefore having a lower consumption etc.

    But I honestly wouldn’t worry too much about “what” the SAC number is, but instead “when” am I likely to need to do something.

    Let me know how that sounds 🙂

    1. Scott Steinbright

      I totally dig that cylinder SAC rate table idea! Nice

      Is it true that in order for a computer to display the data from 2 transmitters simultaneously (like in a sidemount config.), the transmitters must have different sync rates? Oceanic appears to do this (grey vs. yellow transmitters), but Ratio computers don’t. What is your understanding on this?

  3. Vas Proud

    Hi Scott,

    Yes, this is what I have read and understand also. The frequencies used in underwater transmission are not very different to be reliable, so instead, some use a timing style of transmission to send data – this is why the transmitters need to be different for the two tanks (e.g Shearwater recommend one grey and one yellow for the Perdix).

    Ratio transmitters have a user configurable channel you can set them to (31 channels to choose) so the same physical transmitters can be used for the tanks – just with different channels set on them.

    Do take a look at the manuals for these,

    Do also note that both these vendors state that the transmitters should only be used in addition to a regular mechanical SPG!

    Let me know how that sounds. Cheers

    1. Scott Steinbright

      Thank you for the link to Ratio’s transmitter manual (I could have looked that up myself, I guess. Haha!).
      The Ratio system has an impressively rich set of features.

      The only time I use a transmitter is during OW classes and that’s always in a single tank config. with an SPG.
      Using transmitters in a doubles or sidemount setup never really appealed to me because of the additional “catch point”, the durability of the transmitters, and knowing that some of my dive buddies have experienced connectivity issues in the past (older computer systems). But it looks like they’ve developed the communication technology a bit.

      Thanks again 🙂

  4. Brock Morrell

    Thanks Steve and Vas for this video! I had been curious to see if Steve’s thoughts had changed over the last few years.

    I’ve been using the Air Integrated Sensors (AIS) with my Teric for about 18 months now. The additional data like SAC after the dive is nice to have but not need to have. The absolute biggest benefit I have found was in low viz and dark environments, the ability to have the information immediately in front of my eyes at a moment’s glance. The display on the Teric is definitely easier than shining a torch on my spg.

    I do still keep two spg’s with me (or close by) when out diving. At the start of every dive, while pre-breathing, I watch the Teric display to ensure that it is changing with my breath. If there is a problem, I can remove the AIS and replace with SPG. If I’m on a dive and experience a failure of the AIS, I end the dive and replace with SPG. I should also point out that both my AIS (left cylinder / right cylinder) are still on a 6″ hose, just as my SPG would be. In my opinion, this reduces the potential stress / accidental damage on the AIS, and eliminates potential hose routing problems at the 1st stage.

    I am in the process of adding a Perdix AI as my back-up computer. Shearwater has confirmed that both the Teric and Perdix can communicate with both AIS sensors at the same time. If my computer fails, the other computer will still display the information.

    This may not work for everyone but I am happy with this set-up. Thanks again for the new video.


    Hello, guys.

    Definitely, food for thought. My Perdix provides a ton of information revealing that one can hardly know enough; SAC rates are just the tip of the iceberg. When I started diving a few years ago, I was taught that it was ok to “evolve” towards new technologies to find support/redundancy, but that one should never replace the “classics”, such as depth and pressure gauges or compasses (not to mention dive tables). Today, it is common to see fellow divers substituting them completely with dive computers.

    In the case of sidemount, I have seen a variety of set up’s around, such as the one appearing (approximately, on minute 6) of this video; teaming pony spg’s on one side of the first stage with transmitters on 6″ hoses on the other; or even with no SPG’s at all (transmitters only; either connected directly to the first stage or on 6″ hoses).

    How would you advice (or not) to set up Apeks DST first stages utilizing both, SPG’s and Shearwater transmitters?


    1. Steve Martin

      Hi Jose, Thanks for feedback I also agree that teaching dive tables now is just not needed. Time is much better spent having the diver learn the real skills they need in the water and if they are only learning over a few days then honestly learning tables will not improve their diving underwater. In the video you watched there is a photo of a HP fixed angle adaptor, I would suggest that for having the transmitter work with your DST first stage, or a short flexible HP hose, you just want to aviod clutter around the valve handwheel and chest area as much as possible. I would still have the SPG pointing down and not sticking up in the air. Cheers, Steve

  6. Keith Seiser

    Using AI in the past I found that multi tank monitoring was just that monitoring. No matter what tank you had selected the computer ran off of sensor #1 for all calculations #2,3,4 was a remote reading of others tanks and not used in any calculations of the computer wearer. If that has not changed then when using AI the only useful data when selecting other sensors is PSI and nothing more. Gauges seem to be much more reliable in that aspect.

  7. Rob Bulman

    Hi Guys,
    Love the new video’s. For over the last year-and-a-half I have been diving sidemount with two Shearwater transmitters with the Teric and Perdix and both of them displaying the air pressure on the home screen. I have the transmitters on a short 4 inch high pressure hose in the traditional spot you would put the SPG, but for a backup on the top side high pressure port I have a little button SPG, it only takes up about an inch so you don’t even know it’s there but it’s just nice to know is there but I have never is it. With those transmitters just make sure you have good batteries in them you’ll never have an issue.
    Thanks Rob.

  8. David Keith

    Hi guys. Great videos! My thoughts are these… I work as a professional pilot. When glass cockpits were first introduced many pilots didn’t trust the computer “painting” their gauges. Now it’s the standard and very few if any commercial jets have “steam” gauges. I think the diving industry is going through the very same transition, the tech is there but convincing divers it’s not voodoo is the challenge. I have used the Shearwater Perdix AI for several years without a single failure. I now use Garmin MK2i with the sonar based transmitters and have all together ditched my steam gauges. I can’t speak for other brands but the MK2i has the ability to include multiple transmitters in gas consumption calculations. I also love having my tank pressures available at a glance. I would argue that having a hp hose, spool and gauge present far more failure points than having an AI transmitter installed directly on the first stage in the same (facing down) orientation. On a different note, I am very impressed with every video so far and VERY happy about my decision to purchase your courses. Keep up the great work.

  9. Neville Douglas

    Hi Steve and Vas, it’s very interesting, thank you for posting this video, I have been using the shearwater Predix AI for just over a year with two transmitters (pre Covid19), the transmitters are also paired with my Oceanic VTX dive computer, and both are connected to my rights and left side transmitter’s, initially I was using the SPG with the transmitter’s via a splitter and then eventually I moved over to the transmitter on a four inch hose , and then ultimately I went over to just using the transmitter fitted into the first stages, I figured that if I had the transmitter on a hose and the hose failed I would lose a lot of air very quickly, so I determined if the transmitter is fitted directly into the first stage if any transmitter got damaged and failed electronically I would not lose all of my air as the transmitter makes a physical plug so to speak. I have not had any issues in regard to signals loss and I have now completed 191 dives with the various configurations that I have mentioned above, that said I still carry a backup drive computer and SPGS, I always check the batteries in my transmitters on a regular basis and brief all buddies on my configuration, I am aware of my sack rate as Vas mentioned and dive conservatively, moreover, I ensure that I keep the air pressure balanced between my cylinders and so if there was a failure I would know the gas content of either cylinder , but as you say at any failure point I would turn the dive, I have found that the transmitters that work with the Oceanic dive computer also work with the shearwater, my biggest gains was removing the clutter of splitter the hose and the SPG, in that I removed 400gms of weight from the top of my cylinders thus not needing heavier fins to compensate, I found this beneficial whist diving in Palau in a 3mm wet suit as I did not need additional counter balancing weight or heavier fins whist there, that said I am not expert, I just followed your videos and did the weight check locally before my tip, I was the only sidemount diver out of 30 divers and never became that diver.

  10. Gary Spechko

    I bought a Ratio ix3m and transmitter earlier this year and took it to Belize last month. I had a number of issues with it:
    – it didn’t show the tank pressure until I was at depth
    – on two dives it showed the pressure from someone else’s transmitter (I assume – it showed 1000+ PSI more than I had) for short periods
    – it lost connection between the transmitter and the computer on average 3 times per dive.
    – it was very difficult to change the channel it communicated on. I’d set it to a new channel on the boat and it would revert to channel 0 for the dive.

    I had a console computer (oceanic pro plus 3) connected as well, so I could always fall back on that for an accurate reading. But I was quite unhappy with the transmitter’s performance in general.

    I contacted Ratio support, and they told me to increase the gain from 0 to +2 to fix the loss of connection.

    I won’t trust a transmitter without an SPG for the foreseeable future.

    1. Steve Martin

      Hi Gary, wow sorry to hear this and thanks for sharing with us. It is literally the opposite experience to Vas and myself regarding our use of the Shearwater transmitters, they have been incredibly reliable. What you say is bad news for ratio computers, for sure. Cheers, Steve

  11. Alexey Alvianskiy

    Thanks a lot for this video, it brings required clarity to transmitting technology. In addition to what’s been said i would add one another idea: wireless transmitters as a technology are more complex than mechanical spgs. So far I could explain myself why would I add this additional complexity, what extra benefit does it bring.

  12. Csaba Juhasz

    Hi guys. For a sidemount diver, how would you suggest to install the transmitter and the spg using them at the same time? I use Apeks DST 1st stage. Where would you put them? Hose or without a hose, etc. At the moment my spg stays the old position, the hose facing back. The transmitter on a hose facing forward.

    1. Steve Martin

      Hi Csaba, personally I choose to use either SPG or transmitters not both combined. If I was to use combined then SPG points down as normal and transmitter would use the top HP port, guess you have to see what is needed as 1st stages will differ some will allow and others make it hard or not possible without adding a short HP hose. This post and comments on post will really help you https://www.facebook.com/sidemounting/posts/pfbid025jsRrjWbci3BCmUJnt7uGNXYDwvWNk3KAjrAP7mJCzj6X48pHLnoveQp94QFEzrkl. Regards, Steve

  13. Christopher Juniker

    I am starting out sidemount diving, and while doing backmount I have always used my Garmin Mk2I with the T1 transmitter. I actually bought a second transmitter to use with sidemount but didn’t see any opinions on this particular brand in either of your transmitter videos. It is at the most popular computer where I am diving (Monterey, CA USA), so would love to hear your opinions of it.

    1. Steve Martin

      Hi Christopher, to be honestl I have not used the Garmin computer or dived with anyone using it sorry. I am sure if you look on YouTube there will be some reviews about it. The good news is it seems alot more manufacturers are making AI computers and transmitters these days. If you do find out any good information please share it with us all here. Regards, Steve

      1. Christopher Juniker

        I have used it for about 400 dives now in back mount, and have had 3 XSscuba short hoses fail in that time due to strange bubbling issue and apparently there has been a recall on these hoses, but have never had the transmitter fail in that time. I have switched to the metal style of hoses. It seems very reliable, and I like it so much that I bought a second one so that I could use it for side mount diving. I plan to just use the transmitters like you said in a video rather than introducing extra failure points by using SPG+transmitter. The only thing I am doing different is tucking the transmitters into the hose retaining bands in order to keep them out of harms way.

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