Question: Rec mode MOD

[tcoen]

I have a question regarding MOD on rec mode with Perdix ai. It seem that the computer does not give actual MOD ppO2 1.6 at FO2 .21. The computer gives a max depth of 50m rather than 66.1m. I am curious about the computer, not agency standards. Perhaps my setting are incorrect.

Edited as Perdix

Hi Charlier,

There are two settings that affect MOD in Rec Mode. First is the max PPO2 that can be set on the gas setup screen (e.g. 1.4, 1.6, etc). The second is the Max Depth, that is set in the Adv Config page. This can be set up to 165ft/50m

The MOD is the more restrictive of the two. So for example, a max PPO2 of 1.4 would result in air having a MOD of 187ft/56m. But if the Max Depth is set less than this (default is 130ft/40m), then this more restrictive MOD is used. On the gas setup page, the MOD will display grayed out when it is being controlled by Max Depth rather than Max PPO2.

This video demonstrates this (it shows the Petrel, but the operation is the same on the Perdix):

The defaults and maximum values were chosen based on generally accepted recreational guidelines and other limits such as narcosis. As others mentioned, they are warnings only (although ones we believe divers should respect) and won't cause lock-out. Or the technical mode can be used which does not have MOD warnings (other than high PPO2 warnings).

Best regards,
Tyler Coen
Shearwater Research