ScubaPro Chromis Display Question

[kablooey]

Just made my first dives with my new Chromis.
Overall I'm very happy with it, but one thing is bugging me.

During my dives, while I'm ascending, the very top display line seems to scroll through a series of various depths. From memory, these depth read-outs start at around 100 ft, then follow with a series of about four seemingly random depths.

I've noticed this on dives as shallow as 40 ft max, and as deep as 100 ft. Perhaps this is something to do with deep stops? I've read through the manual several times and I'm still confused.

Does anyone know the Chromis, and can tell me what this display is trying to tell me?

K.

 

[CandiveOz]

I believe its your PDIS (Profile Dependent Intermediate Stop), page 31 of your manual. You'll notice it starting around 8 metres (26 feet) and slowly increases since its based on dive time and depth. Its unique to a deep stop which is only based on depth and doesn't take into consideration time at depth and is simply calculated as half your depth to the first deco stop or the surface.

PDIS is a specific stop for 2 min to allow off-gassing of the intermediate compartments while deep stops focus on the fast compartments. If you skip your PDIS you are not penalised. You can also turn this feature off in the settings. In the following post I provide screen shots to demonstrate how it works;

Deep Stops Recreational Divers.
Its a dive to 30 metres for 15 min where the PDIS kicks in at the 9 min mark of the dive for 8 metres and then increases to 12 metres before I start my ascent. When I reach the PDIS depth of 12 meters you will see in the bar chart the 3rd red compartment bar (on gassing) turn to green (off gassing). That's the idea, to give time for the intermediate compartment to off gas. The third bar in the graph represents compartment 3 in Buhlmann ZHL-8 algorithm or compartments 5 & 6 in Buhlmann ZHL-16.

 

[kablooey]

Thank you for your thoughtful reply.

You're probably right about it being related to PDIS, but the thing that confuses me is the scrolling.
If I understand your explanation correctly, is the Chromis suggesting I make brief stops at the depths seen in the scrolling, separate from the half-max depth deep stop?
How long? A minute?
That would make sense, but it's not explained well in the manual.

I've made all the deep stops in the cases where the two-minute timer activates and is displayed.
No timer has displayed until I've reached about half my max depth, although the top line continuously scrolls through depths deeper and shallow than that.

K.

 

[CandiveOz]

Unfortunately I don't own a Chromis but I do have a Galileo Sol and basically they should work the same. PDIS is only one stop for 2 minutes not a number of stops. I wonder if what you are looking at is Microbubble levels. Do you know what Microbubble level (MB) you have your computer set? It goes from MB0 (MB turned off) to MB5 (most conservative setting). But I don't think the MB levels scroll either so the phenomena is a bit odd. Hopefully someone with a Chromis can contribute to this post. In the meantime, turn off PDIS and set the MB level to 0 (zero) and see if that stops the scrolling.

 

[CandiveOz]

This got me bugged so I decided to go back to the user manual. Forget what I said about Microbubble levels. This happens when you are ascending. It is not depth. I believe it is your ascent rate as a percentage. Page 37 of the user manual.

 

[kablooey]

Thank you.
I'm going to turn PDIS off and set the MB level to 0, and see what happens.

K.

 

[WileDiver]

Hi there !

Can you explain to me how to disable PDIS on the Chromis ?

thx