Suunto D6 showing 76.7 metres' depth

Suunto D6 in full panic mode (part I)

On the second dive we did at Doodles during our trip to Ponta do Ouro, something happened that caused my dive profile to look like this (click on the image to embiggen):

Profile (from MacDive) of a dive at Doodles
Profile (from MacDive) of a dive at Doodles

Fortunately that something was not me falling down an 89 metre deep hole in the ocean floor whilst breathing off a 12 litre cylinder of air, 45 minutes into a dive. It was something going wrong with (we think) the pressure sensor of my Suunto D6 dive computer. I have had the computer for a few years, and apart from the compass appearing to have packed up, it has been a fantastic device.

The first inkling of trouble that I had was when the computer started beeping at me, and when I looked down to see what was up, it said we were at 89 metres. Sunlight was falling on me, so I thought this unlikely. I checked with Christo, and he didn’t think we were that deep either. Nor did his computer. Fortunately I had been diving with a group for a few days, and we were well within our decompression limits at a depth of 14-15 metres. Losing the computer three quarters of the way through a dive wasn’t the disaster it could have been.

I took this picture shortly after the beeping started. The display at the top of the screen shows that the computer is reading 76.7 metres. The maximum depth of 89.0 metres shows at the bottom left. The bottom right shows the oxygen partial pressure, at 1.9. This is greater than the 1.2 limit that I have set for myself inside the computer. The computer thinking that I had rapidly exceeded the maximum PPO2 is probably the initial cause of the beeping I heard.

Suunto D6 showing 76.7 metres' depth
Suunto D6 showing 76.7 metres’ depth

In the middle of the screen you can see a large number 8.0, which is the depth to which the computer wants me to ascend in order to do a decompression stop. Next to that number is an arrow below two horizontal lines, and the number 35. This is how long I should stop at 8 metres in order to fulfil the calculated decompression obligation.

The D6 thinks we have ascended to 47 metres now
The D6 thinks we have ascended to 47 metres now

After a few minutes (I was actually busy ending my dive with a 5 metre safety stop) the computer believed I had ascended to 47.3 metres. By that stage it wanted me to go to 11 metres for a 45 minute stop. When I surfaced after about 60 minutes of dive time, the computer stayed in dive mode, thinking that I was still at a depth of about 35 metres. It continued registering a slow, quite smooth ascent for another hour and a half, as seen in the dive profile above.

The computer was still very grumpy when it took itself out of dive mode in a mug of warm water in the bathroom of Planet Scuba, while we were eating a post-dive lunch. The ascent profile it registered did not fulfil the calculated decompression obligations, and it showed that I had violated my decompression ceiling (either by taking too long to ascend to start the stops, or by not spending enough time at the stop depth).

I have put myself briefly into deco a few times (usually during days of repetitive diving during dive trips, and once or twice in Cape Town with two relatively deep and long dives in a day), so the readouts from the D6 on this dive are not unfamiliar to me. I have never before, however, seen such large numbers or heard so much beeping! I have always corrected the situation by ascending a little way, which removed the decompression obligation and returned the display to what I am familiar with as a religiously recreational, no-decompression diver. In this case, the D6 was doing its own thing and nothing I did seemed to influence the depth reading it gave.

I found this to be an excellent opportunity to re-familiarise myself with the behaviour of the Suunto D6, and also to see what all the error messages look like on the dive profile when I downloaded the computer into the MacDive software I use for electronic dive logging. The story does not end here – if the computer did not think I was dead from DCI, it wasn’t going to let me dive any time soon – check back tomorrow (or the day after).

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Clare

Lapsed mathematician, creator of order, formulator of hypotheses. Lover of the ocean, being outdoors, the bush, reading, photography, travelling (especially in Africa) and road trips.

2 thoughts on “Suunto D6 in full panic mode (part I)”

    1. I soaked mine in warm fresh water and it seems to have resolved itself (I have done a few shallow dives with it since), but I am not sure that I trust it very much any more! Try give it a soak in case it is crusty with salt or has dirt on the pressure sensor… If that doesn’t help you’ll need to get it looked at by a professional!

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