The precise measurement of insuline volume contained in an insuline pen is crucial for both the patients and the doctors. The development by Valtronic, with the collaboration of the EPFL, of a measurement device with a 10uL resolution, is the focus of this master thesis. This device is called a radio cap. The insuline pen is inserted inside the radio cap. The cap is made so that the system {cap+insuline pen} resembles a waveguide, wherein the external conductor would be the copper envelope and the central conductor would be the insuline solution. The cap would carry a radio transmitter at its tip in order to send a radio wave through the cap, as well as a radio receiver.