A drug delivery device comprising: a housing; a plurality of contacts; a rod (414, 800, 802) disposed within the housing, wherein an outer surface of the rod is provided with a first thread having a first pitch and a second thread having a second pitch and wherein the first thread is configured to engage with a threaded aperture of the housing such that the rod rotates in a first rotational direction and advances in a first axial direction relative to the housing when an axial force is applied to the rod during a drug dispense; and an encoded member configured: to be rotatably supported inside the housing; to be threadably engaged with the second thread of the rod and to be rotatable with respect to the rod; and to be axially constrained with respect to the housing such that axial advancement of the rod in the first axial direction relative to the housing causes rotation of the encoded member, wherein the second pitch is adapted such that the encoded member rotates at a higher angular velocity than the rod during the drug dispense, wherein an outer surface of the encoded member is provided with a plurality of tracks together forming an encoder, each track comprising conductive segments and non-conductive segments and wherein the encoded member is supported in the housing such that each track is engaged by a respective one of the plurality of contacts. a housing; a plurality of contacts; a rod (414, 800, 802) disposed within the housing, wherein an outer surface of the rod is provided with a first thread having a first pitch and a second thread having a second pitch and wherein the first thread is configured to engage with a threaded aperture of the housing such that the rod rotates in a first rotational direction and advances in a first axial direction relative to the housing when an axial force is applied to the rod during a drug dispense; and an encoded member configured: to be rotatably supported inside the housing; to be threadably engaged with the second thread of the rod and to be rotatable with respect to the rod; and to be axially constrained with respect to the housing such that axial advancement of the rod in the first axial direction relative to the housing causes rotation of the encoded member, wherein the second pitch is adapted such that the encoded member rotates at a higher angular velocity than the rod during the drug dispense, wherein an outer surface of the encoded member is provided with a plurality of tracks together forming an encoder, each track comprising conductive segments and non-conductive segments and wherein the encoded member is supported in the housing such that each track is engaged by a respective one of the plurality of contacts. to be rotatably supported inside the housing; to be threadably engaged with the second thread of the rod and to be rotatable with respect to the rod; and to be axially constrained with respect to the housing such that axial advancement of the rod in the first axial direction relative to the housing causes rotation of the encoded member, wherein the second pitch is adapted such that the encoded member rotates at a higher angular velocity than the rod during the drug dispense, wherein an outer surface of the encoded member is provided with a plurality of tracks together forming an encoder, each track comprising conductive segments and non-conductive segments and wherein the encoded member is supported in the housing such that each track is engaged by a respective one of the plurality of contacts.