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Tamas:1atm in fresh water is 33 feet while in salt water 1atm is 34 feet.....so in short 1 foot dfference every atm
The example above is for going down to a marked 68' in salt water(34' ATM X 2=68' actual/salt water), with a gauge that is calibrated for fresh water(33' per ATM X 2=66').Chad Carney:A gauge or computer reading in fresh water will read deeper, not shallower.
In the above example both gauges sense 3 atm of total pressure at 66' in seawater, and the salt water gauge will read 66', but the freshwater gauge displays 68 feet.
For a computer it's of no consequence, because it's not being compared to tables. It's time at pressure that the algorithm is calculating.
Chad
JustinW:I believe Chad has it correct. It doesn't matter because the computer is calculating time and pressure. The depth is of no consequence to the equation.