The goal of this master thesis in Industrial Design Engineering was to develop a new graphical interface with a focus on usability for the medical device CELDA System as the graphical interface has not undergone any revisions regarding usability. The research questions for this work covered areas to identify design weaknesses on the current interface regarding usability, how those design weaknesses can be addressed,and how the user needs can be incorporated. For this project, the process "Usabilityengineering process" was applied to identify and minimize user errors. The process also involved using creative methods to generate a wide range of ideas. The identified design weaknesses in the current interface are, for example, unclear visual hierarchy,unclear structure with somewhat difficult navigation, and the boxes used in the designcontribute to a visual cluster. These weaknesses were removed using design principles,which were partially confirmed by the user test. The new interface has a clearer visual hierarchy in the form of text and object sizes, improved structure (for example, fewerboxes and gridlines).