Sensing systems are disclosed for determining the relative rotational movements of members of a medication delivery device which are proportional to the amount of a dose set and delivered by the medication delivery device. The sensing system comprises a first sensor component secured to a first member and a second sensor component secured to a second member. During dose setting, the second member is coupled to a third member which rotates relative to the first member in proportion to the dose set. During dose delivery, the second member is coupled to a fourth member which rotates relative to the first member in proportion to the dose delivered. The sensing system separately detects the relative rotational positions of the first and second sensor components during dose setting and dose delivery, and provides outputs used to determine the amounts of the set and delivered doses. The sensing system outputs this information to a controller which determines the amount of the dose set and delivered. Related medication delivery devices and methods are also disclosed.
