An apparatus for detecting the engagement of a consumable in a printing device includes a consumable cartridge having a rotatable member carried by the cartridge, and a drive member configured to engage and rotate the rotatable member. A proximity sensor positioned adjacent an engagement interface between the rotatable member and the drive member generates an output signal variable with the distance between the rotatable member and the drive member. Data that is stored in memory provides at least one predetermined set of characteristic values of the proximity sensor output signal versus distance between the rotatable member and the drive member, where the at least one characteristic value of the proximity sensor output signal is indicative of engagement between the rotatable member and the drive member. Processing circuitry coupled to the proximity sensor and the memory determines when the rotatable member and drive member are engaged.