Drug delivery device with dose capturing module

A drug delivery system is provided comprising drug expelling means adapted to expel a set dose from a drug-filled cartridge, the expelling means comprising a rotational member adapted to rotate relative to a housing and corresponding to a set and/or expelled dose, the system comprising a sensor adapted to detect a set and/or an expelled dose. The sensor comprises a first portion mounted to and rotating with the rotational member, and a second portion comprising a second rotary sensor part mounted non-rotationally relative to the housing. The first portion comprises electronic circuitry, and a first rotary sensor part, and the second portion comprises a second rotary sensor part mounted non-rotationally relative to the housing. The first and second rotary sensor parts rotate relative to each other during set- ting and/or expelling of a dose of drug.