A drug delivery device (100) for adjusting and injecting adjusted doses of a drug from a drug filled tank, comprising: a Gray code type detector for detecting the relative movements between a first element (230) and a second element (250), said elements (230, 250) moving relatively during dose adjustment and / or during injection where the Gray code type detector comprises a code track (231a, 231b) arranged in the first element (230 ), the code track (231a, 231b) comprising a sequence of marks that alternates between the first and second states, and wherein the code track (231a, 231b) is associated with several detectors (292a, 292b, 293a, 293b , 294a, 294b, 294c) arranged in the second element (290), each detector (292a, 292b, 293a, 293b, 294a, 294b, 294c) being adapted to detect the states of the marks, characterized in that the sequence of marks consists of areas first and it There are alternatives to the respective first and second states, where each of the first areas has an extension along the extension code track X1 and each of the second areas has an extension along the code track X2 extension, and wherein the various detectors (292a, 292b, 293a, 293b, 294a, 294b, 294c) are provided as at least three detectors (294a, 294b, 294c) adapted to detect the state of said sequence of marks, the at least three detectors being mutually displaced in an direction that extends along the code track (231a, 231b) to provide a reading sequence of a Gray code scheme when the at least three detectors (294a, 294b, 294c) move with respect to the code track (231a, 231b) along the sequence of marks.Un dispositivo de administración de fármacos (100) para ajustar e inyectar dosis ajustadas de un fármaco desde un depósito lleno de fármaco, que comprende: un detector del tipo código Gray para detectar los movimientos relativos entre un primer elemento (230) y un segundo elemento (250), moviéndose dichos elementos (230, 250) relativamente durante el ajuste de la dosis y/o durante la in
