GNGTS 2013 - Atti del 32° Convegno Nazionale

that had to be connected, this turns out to be especially dangerous for the moving of statues inasmuch as high stress can be generated and concentrated near the surface with consequent rupture. Iron or steel pins can be revealed and located with electromagnetic induction techniques even if the location can be sufficiently precise and reliable only when very simple geometries occur: pins parallel to a flat surface (pachometers for concrete rebar detection). On purpose Ground Penetrating radar (GPR) systems and software have been developed to rebar detection and by properly using these systems a 3D reconstruction of the rebar grid is possible. On the other hand, as for the pachometers, single pins of some centimetre length, with a diameter of some millimeter, nearly random oriented in volume with complex geometries such as a statue, cannot be reliably located mainly because of the size of the antennas and the wavelengths of the GPR pulses. Presently the shortest wavelengths that propagate in ornamental stones with GPR are around 5 cm (Vaccaneo et al. , 2004). This means that even if the presence of a metal pin can be detected, its size and position cannot be reasonably estimated. Despite the large amount of mathematical tools developed to process potential field data, the analysis of static magnetic field for testing artifacts is, at our knowledge, not used. Very likely one of the main reasons of this lack of application is due to the small volumes that have to be investigated compared to the larger size of traditionally employed magnetometers, such as fluxgate, proton, etc. However, in recent years we assisted to the development and diffusion of a new type of miniaturized sensor and actuator devices based on the semiconductor technology. These devices, known as Micro Electro-Mechanical Systems (MEMS), include accelerometers, gyroscopes, pressure sensors, displays, microfluidic equipment, optical switches, and magnetometers. Miniaturized triaxial MEMS magnetometers are normally used as digital compasses (in combinations with accelerometers) in consumer applications, such as augmented positioning and navigation systems (to facilitate the dead-reckoning navigation) and mobile smart phones. The magnetometer. MEMS-based magnetic field sensors can offer small-size solution for magnetic field sensing. Smaller devices can be placed closer to the measurement spots, thereby achieving higher spatial resolution. Additionally, MEMS magnetic field sensors do not involve the microfabrication of magnetic material: therefore, the cost of the sensor can be largely reduced. Integration of MEMS sensor and microelectronics can further reduce the size of the entire magnetic field sensing system. Fig. 1 – The STMircoelectronics iNEMO-M1 board (a) hosting the triaxial magnetometer/accelerometer LSM303DHLC (b, within the red circle in a). 170 GNGTS 2013 S essione 3.2