Intermediate 8 minutes
Using your dive computer to plan, not just obey
Planning modes, conservatism, and what to do when an alarm appears
Most divers use their computer like a traffic light: they watch the number, and when it turns red, they go up. But the same device has a mode that answers the opposite, far more useful question: if I want to go down to thirty metres, how much time do I have?
In this article you'll see how to use planning mode, what the conservatism setting actually does, how to interpret the most common alarms, and what to do if your computer fails during a dive trip.
It's the difference between reacting to an instrument and using it to make decisions. The computer holds information that almost no one checks before getting in the water.
Planner mode
Practically every dive computer includes a planning mode that lets you check, before getting in, how much no-stop time you have available at different depths.
Its great virtue is that this calculation accounts for your actual situation: if you already made a dive that day, the planner subtracts the residual nitrogen load you're still carrying. A generic table can't do that without extra calculations.
The practical use is direct: before your second or third dive of the day, check what time the planner gives you at the planned depth. It's common to find that the accumulated load reduces the available time considerably more than expected, and that changes the plan.
It's also worth watching the elapsed surface interval. Many computers show how the available time keeps increasing as the minutes on the surface pass, which lets you decide with good judgement how long it's worth waiting before getting back in.
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