Patent ID: 7448384

Claim:
A method adapted to be implemented in a portable electronic device having at least a first operating mode and a second operating mode, called the dive mode, and comprising in particular a pressure sensor for measuring the value of the ambient pressure (P) and electronic circuits for processing the results of said measurements comprising a time base and at least one memory zone, the method being implemented in said first operating mode for detecting a start of a dive and automatically switching said portable electronic device over to said dive mode when the start of a dive is detected, said method comprising the steps of: a) measuring an ambient pressure value and storing it as a reference value (Pref); b) periodically measuring the value of the ambient pressure (P) at a first frequency (f 1 ), c) periodically calculating the value of the variation in pressure (dP) between the measured ambient pressure (P) and the reference pressure (Pref) at a first frequency (f 1 ) and comparing said pressure variation value (dP) to a predefined value, called the trigger threshold (S) stored in the memory zone ( 7 ), d) if the pressure variation value (dP) is higher than said trigger threshold, then switching over to said dive mode; if not, then continuing to step e), e) comparing, at a second frequency (f 2 ), said pressure variation value (dP) to a predefined quantity (c 1 ), stored in said memory zone, or determined (dPm) on the basis of measured pressure values, said quantity being lower than said trigger threshold (S), said second frequency (f 2 ) being lower than or equal to said first frequency (f 1 ), f) if the pressure variation value (dP) is higher than said quantity, then making a correction to the reference pressure value (Pref); if not, then storing the last measured pressure value (P) as the new reference pressure value (Pref), g) returning to step b).