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 (130, 430, 530), the sense load (130, 430, 530) being operably coupled to the piezoelectric device so that a sensed voltage (90, 94) across the sense load (130, 430, 530) has a phase corresponding to a phase of the piezoelectric device, the circuit being configured to: determine whether the sensed voltage (90, 94) is in phase or out of phase relative to the switching voltage; responsive to the sensed voltage (90, 94) 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 (90, 94) 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 (130, 430, 530), the sense load (130, 430, 530) being operably coupled to the piezoelectric device so that a sensed voltage (90, 94) across the sense load (130, 430, 530) has a phase corresponding to a phase of the piezoelectric device, the circuit being configured to: determine whether the sensed voltage (90, 94) is in phase or out of phase relative to the switching voltage; responsive to the sensed voltage (90, 94) 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 (90, 94) 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 (90, 94) is in phase or out of phase relative to the switching voltage; responsive to the sensed voltage (90, 94) 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 (90, 94) 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.