Tegg:
The biggest problem I have with my cochrans ( I own 2), is not allowing for manual gas switch.
I agree, and this is my only signifigant criticism of the Cochrans, beside the fact that they do not make the information about their algorythm widely available.
Since a lost gas scenario is one we plan for but rarely need to impliment, perhaps it would be nice if they would allow for a manual switch back to the previous gas by putting a piece of metal (knife tip or shears) accross the contacts. I understand their desire to eliminate buttons, but it would still be nice to allow for this.
I am currently using a 3 gas Gemini ( I do not have training in the use of helium) and you can trick the computer into using the gas you want. Since the gemini is air integrated it switches from gas 1 to gas 2 when you stop breathing your back gas and it notices the pressure stops dropping. It switches to gas 3 when the time and depth benchmarks are both met.
If you loose gas 2 simply continue to breathe your back gas, it will see the pressure drop and compute deco based on that gas. If you loose gas 3 and lets say that is 100% O2 you simply make sure the depth benchmark is set for 20 feet, and when you are at your 20 foot stop you level off at 21 feet, this will force the computer to use gas 2. For the computer to know when you have cleared your deco you would need to stay at the 21 foot stop until the computer completely clears you to the surface.
Of course this would not work as well on an EMC-20H for the gas switch to gas 2 since you would not want to stay 1 foot deeper than your first stop on this gas, but the loss of gas 3 thing would still work. At best this is a somewhat awkward work around, the better option would be to allow for a manual override. I do like the automatic gas switch, one less thing to forget. I have never seen a diver fail to make a planned and necessary gas switch, but I have seen divers make the switch but forget to tell thier computer they did.
Mark Vlahos
