System for the non destructive testing of dielectric materials by means of microwave techniques. The sensor is constituted by a narrow band antenna whose resonance frequency depends on permittivity of the media in the region close to the antenna. When the sensor is close to an object, the permittivity of the surface layers of the object itself is determined by the variation of the resonance frequency w.r.t. a vacuum measurement. Thus, we can obtain information about the object structure. Several kinds of sensors have been designed and realized as well hardware devices able to pilot the sensors for the acquisition of the signals to be processed. A software has been also developed to control the hardware devices and to perform data analysis. This software is installed on a PC/notebook to which external components are connected. The system can be employed both in laboratory conditions and on field for applications regarding quality control and the conservation status of manufacts.