A rotary button system (100; 300) for use in a domestic apparatus, comprising: a ferromagnetic plate (110; 310); a button (120) removably mountable at a predefined first distance (dm) from said ferromagnetic plate (110) on a first side of said plate, and rotatable about a virtual rotation axis (105) substantially perpendicular to said plate, and comprising a permanent magnet (122) magnetised in a direction (X, Y) perpendicular to said rotation axis (105); and a magnetic sensor device (130) mounted at a predefined second distance (ds) from said ferromagnetic plate (110) on a second side of said plate opposite the first side, and comprising one or more magnetic sensors for measuring one or more magnetic field components or field gradients, and configured for determining an angular position (a) of the rotary button (120) based on said one or more field components and/or field gradients.