In mass metrology there is a distinction between the different classes of weights, starting from E1, which is the most accurate class, down to M3. To calibrate these weights they must be compared with a weight who is one class higher. Offcourse when you want to calibrate the highest class, E1, there is no higher class to compare to. That is where the density of the mass kicks in. The aim of this project was to use a thermal bath and an EMC comparator to develop a system that could measure the density of a certain weight. To do this a weight will be submersed in water. From the difference that was found between the mass of this weight in water and the mass of this weight in air, the density of that weight can be calculated. The project was executed under the supervision of: -FYI Dr James E. Walsh, DIT (Dublin, IRELAND) -Mr. Rory Hanrahan, NSAI, NML National Metrology Laboratories (Dublin, IRELAND) -Eng. Luc Vanhee, KHBO (Ostend, BELGIUM) The end result is a prototype that meets most of the requirements. Nevertheless, minor improvements such as more automation, are always possible.