A preliminary test on the feasibility of locating an iron restoration pin in a statue by measuring the TMF anomaly with a triaxial MEMS magnetometer

We made a model of a “restored arm” with a bioclastite cylindrical sample (height= 18 cm; diameter=10 cm) in which an iron pin (length= 9 cm; diameter= 5 mm) was inserted out of the sample axis and obliquely (Figure 2a). A rotating platform surrounded by a graduated scale allowed us to rotate the sample in step of 10°. A sliding beam was used to move vertically the magnetometer so that, combining the two movements, the sample was scanned along horizontal circles 1 cm apart along its height (Figure 2 b) . At each measuring point we recorded 50 times at 50 Sample/s the three magnetic components (Vertical, Radial and Tangent) with the height and the angle. At each point mean, standard deviation and standard deviation of the mean over the 50 readings were calculated and the means were then taken as raw data. With this experimental setup, aimed to perform a preliminary test of the effectiveness of the sensor, the pin rotated within the sample and was always south of the sensor, therefore we did not get the reconstruction of the magnetic field around the sample as it would be in an acquisition, for example, around a statue arm.