The present invention relates to a circuit device for a metered dose inhaler and an assembly thereof. The circuit device is adapted to be removably mounted on a metered dose inhaler and operably connected with the metered dose inhaler. The circuit device comprises: an acoustic sensor a cylindrical protrusion circumscribing the acoustic sensor, the cylindrical protrusion adapted to be received in a first mechanical interface of the metered dose inhaler and defining an acoustic-path between the acoustic sensor, a canister adapted to hold a medicament and an opening of the metered dose inhaler and a processor communicatively coupled with the acoustic sensor, the processor adapted to: receive a signal from the acoustic sensor indicating dispensing of a medicament from the opening via the acoustic-path during inhalation and determine at least one parameter associated with the dispensing of the medicament based on the signal. <>
