An atomizer for a liquid comprising: a housing; a power source ; a piezoelectric device operable by a switching voltage ; and a circuit including a sense load , the sense load being operably coupled to the piezoelectric device so that a sensed voltage across the sense load has a phase corresponding to a phase of the piezoelectric device , the circuit being configured to: determine whether the sensed voltage is in phase or out of phase relative to the switching voltage ; responsive to the sensed voltage being in phase relative to the switching voltage when the switching voltage is provided at an operating frequency , make a change to the operating frequency by a predetermined first value; and responsive to the sensed voltage being out of phase relative to the switching voltage when the switching voltage is provided at the operating frequency , make a change to the operating frequency by a predetermined second value, characterized in that , the circuit is further configured such that if the predetermined first value corresponds to an increase in value of the operating frequency , the predetermined second value corresponds to a decrease in value of the operating frequency , and if the predetermined first value corresponds to a decrease in value of the operating frequency , the predetermined second value corresponds to an increase in value of the operating frequency . a housing; a power source ; a piezoelectric device operable by a switching voltage ; and a circuit including a sense load , the sense load being operably coupled to the piezoelectric device so that a sensed voltage across the sense load has a phase corresponding to a phase of the piezoelectric device , the circuit being configured to: determine whether the sensed voltage is in phase or out of phase relative to the switching voltage ; responsive to the sensed voltage being in phase relative to the switching voltage when the switching voltage is provided at an operating frequency , make a change to the operating frequency by a predetermined first value; and responsive to the sensed voltage being out of phase relative to the switching voltage when the switching voltage is provided at the operating frequency , make a change to the operating frequency by a predetermined second value, characterized in that , the circuit is further configured such that if the predetermined first value corresponds to an increase in value of the operating frequency , the predetermined second value corresponds to a decrease in value of the operating frequency , and if the predetermined first value corresponds to a decrease in value of the operating frequency , the predetermined second value corresponds to an increase in value of the operating frequency . determine whether the sensed voltage is in phase or out of phase relative to the switching voltage ; responsive to the sensed voltage being in phase relative to the switching voltage when the switching voltage is provided at an operating frequency , make a change to the operating frequency by a predetermined first value; and responsive to the sensed voltage being out of phase relative to the switching voltage when the switching voltage is provided at the operating frequency , make a change to the operating frequency by a predetermined second value, characterized in that , the circuit is further configured such that if the predetermined first value corresponds to an increase in value of the operating frequency , the predetermined second value corresponds to a decrease in value of the operating frequency , and if the predetermined first value corresponds to a decrease in value of the operating frequency , the predetermined second value corresponds to an increase in value of the operating frequency . <EOS>