The present invention relates to a monitoring device (10) arranged to be operably connected to a medicament delivery device (12), said medicament delivery device (12) comprising a manually operated movable dose activation element (20), said monitoring device (10) comprising an electronic circuit (42), said electronic circuit (42) comprising an optical sensor (68), wherein said optical sensor (68) is positioned in relation to said dose activation element (20) so as to detect a manual operation of said dose activation element (20) from an initial position； said electronics circuit further comprising a vibration sensor (70), wherein said vibration sensor (70) is positioned in relation to said medicament delivery device so as to detect specific vibration spectra produced by the medicament delivery device when said dose activating element (20) is operated, wherein said electronic circuit (42) comprises computing elements capable of correlating the information from the optical sensor (68) with the information from the vibration sensor (70) when said dose activation element (20) is operated in order to register when a correct dose has been set.
