DATA COLLECTION APPARATUS FOR ATTACHMENT TO AN INJECTION DEVICE

Data Collection Apparatus for Attachment to an Injection Device A data collection device comprising a first portion configured for attachment to a rotatable dosage knob of an injection device in which the dosage knob is configured to rotate as medicament is expelled from the injection device, a second portion rotatably coupled with the first portion, wherein at least part of the second portion is movable axially relative to the first portion. The second portion comprises a button which is rotationally fixed relative to the second portion, and moveable between an extended position and a depressed position. The button and second portion are configured such that moving the button to the depressed position causes the second portion to move axially relative to the first portion. A sensor arrangement is configured to detect rotation of the first portion relative to the second portion. A processor arrangement is configured to, based on said detected movement, determine a medicament amount expelled by the injection device. The data collection device comprises a one-way mechanism engageable with the first portion and configurable to permit relative rotational movement between the button and the first portion in a first rotational direction and to prevent relative rotational movement between the button and the first portion in a second rotational direction opposite to the first rotational direction.