How to read tank pod pressure arch display in dive mode

garethm

Since the Ocean cannot display compass heading and tank pressure numerical value at the same time, I’ve been trying to use the arch tank pressure display to estimate remaining gas. But I’m struggling to make sense of the display. I’m in the US so have the watch set to ft / psi.

From the manual:
Tank pressure: The arch shows the tank pressure if the watch is paired with a Suunto Tank POD. The range is determined by the Tank POD pressure reading value at the start of a dive and it can be 250 bar or 350 bar. The bars on the arch always represent 50 bar or 500 psi depending on unit settings. The colors represent certain parts of the range and they are always fixed to:
• Red : 50 bar / 750 psi or less
• Orange: 51 bar – 80 bar / 750 psi – 1000 psi

Per the above, each of the bars should be 500 bar / 500psi. However it also mentions that the red colored bar is 750psi which is confusing.

Here’s an example – my tank has 1746psi according to pre-dive screen:

In dive mode, switching the arch to tank pressure display – I see the following:

If each bar is 500psi, then this is telling me just under 1250psi, so that’s wrong.

The manual says the red bar is 750psi, but this also doesn’t make sense since the orange bar should show up to 1000psi per the manual, but the orange portion reads more like 1200psi (~1.6 * 750). And I would read the tank pressure mark just before the 12 o’clock position to be just under 1875psi (2.5 x 750) – this is also not correct – and also way too much mental calculation to do during a dive.

Is the manual wrong? Is there a bug? Maybe both… Can anyone explain how to read this?

Perhaps this is more intuitive when the units are set to bar with everything divisible into 50, but it’s still not easy to see at a glance when needing to know the numerical value of gas left, e.g. to share that with a buddy.

I would much rather see this outer arch displaying a marker showing compass north / allow marking a heading – and have both compass heading numerical value AND tank pressure numerical value displayed at the same time. There’s a lot of blanks space on this dive screen. I posted that feedback on the dive mode screen thread already.

Frank Scholer

Hi @garethm,

I think - don’t know for sure, though - that it’s a small error in the manual. In my opinion, it should not state “The bars on the arch always represent 50 bar or 500 psi depending on unit settings.” but “The bars on the arch always represent 50 bar or 725 psi depending on unit settings.”.

If the pod sends a pressure under 250 bar, I expect each segment to be 50 bar or 725 psi. Your 1746 psi would then match the position on the arch (2 * 725 + a little bit less then the half of 725, let’s say 300 equals to 1450 + 300 = 1750)…

This is at least how I read this display. On the other hand: I did 25 dives with the ocean this summer and never used the arch display for tank pressure or any of the other options (calculating under water is cumbersome) but did just use the switch window. So the only useful application of the arch would be - for me - a graphical compass.

Hope that helps, Frank

garethm

Thanks @Frank-Scholer, that does make sense. I’d say that’s a pretty significant error in the manual, this is the measure of air remaining after all!

Agree with you re. the current arches not being helpful in general. Since I have to choose between compass heading and tank pressure display, I’m just trying to make use of the arch as a workaround to that limitation. The more I think about it, placing this cognitive load on the user during a dive seems quite problematic and a questionable design decision from a safety perspective.

A graphical compass (with the heading numerical value also always displayed) would be a much better use of this space, with the tank pressure value only shown numerically (at the same time as heading!).