Low air warning device for scuba divers

Claim 1

A low air warning device for alerting a scuba diver when the pressure of air in an air tank being used by the scuba diver falls below a predetermined level; said device producing an audible signal within the range of hearing of the diver when the pressure of air within the air tank falls below the predetermined level; said device comprising: a) an electrical energy source providing electrical power for the operation of said device; b. a piezoelectric speaker element operable for producing said audible signal wherein said audible signal has a frequency within the range of human hearing; c) a central processing unit (CPU) providing: (i) input means for receiving an electrical signal from an air tank pressure sensor, (ii) means for comparing said electrical signal with a reference signal, said reference signal being equal to the electrical signal produced by said air tank pressure sensor when the pressure of air within an air tank is at said predetermined level, and (iii) output means operable for controlling the production of said audible signal by said piezoelectric speaker element; d) a water conductivity switch comprising two stainless steel contacts in electrical communication with said CPU operable for causing electrical power to be supplied to said CPU when said device is immersed in water; e) said air tank pressure sensor in electrical communication with said CPU, said air tank pressure sensor being operable for presenting an electrical signal to said input means of said CPU; and f) a waterproof outer casing; and wherein said electrical energy source, said CPU, said water conductivity switch, said air tank pressure sensor and said piezoelectric speaker element are all housed within said waterproof outer casing and wherein said piezoelectric speaker element produces said audible signal only when said electrical signal is less than or equal to said reference signal.