## 4 Discussion  
A low-cost portable device capable of measuring detachments and delamination to help conservators in analyzing the state of conservation of an artefact has been designed. Tests were performed on several test objects to simulate various usage scenarios. We made both laboratory models (as in Figures 8 and 12) and real models (as in Figure 9), and we also measured a real object, as in Figure 10. All these tests confirmed the validity of the system and its flexibility in use in situ. In Figure 8 we show the measurement carried out on a test object made using a 20 \(\times\) 20 cm sheet of PMMA with a thickness of 4.8 mm, glued with cyanoacrylate glue to a base consisting of a white tile of the same size. To obtain the gaps, paper thicknesses were used, to obtain a gap depth less than 1 mm. Using this method, three pseudo-rectangular cavities were created. The data were then processed using the contour map technique, and the recognition of the three pseudo-rectangular areas was evident. Only one of the three rectangles is not well defined, probably because the paper thicknesses introduced in this area were not sufficient to create a cavity depth greater than 0.8 mm, or, more likely, because the surface of the tile was not uniform. In Figure 9 we show the measurement carried out on a test object made using the same type of PMMA sheet used above, glued to a base consisting of a tile covered with quick-setting cement mortar. The evident non-uniformity in the thickness of the cement mortar revealed few points of actual contact with the PMMA slab. Furthermore, the bonding of the plate to the mortar was only partial, and in fact this circumstance was measured. The data were then processed using the contour map technique and the CTT procedure, with a fusion of data. In this case the recognition of the zones is less evident, also because the measured mesh is much more complex, closer to measuring a real surface full of defects. Using this type of test object it is possible to highlight with certainty the points of effective intimate contact with the PMMA plate. In this type of test object it is not possible to define in advance the maximum dimensions of the delamination and not even the dimensions of the cavities that are artificially created. In fact, it represents the exact opposite case to the one previously examined, and also the most difficult to interpret even if it is sometimes closer to reality. The measurements performed on the ceramic tiles in Figure 11 allowed us to establish the limits within which the audio measure can be considered reliable. As mentioned, these limitations are mainly due to the hardware used and can be increased by improving the specifications of the used components at the expense of their cost. The tiles in Figure 11,  
Figure 13: A measurement performed repeatedly hundreds of times on two points, alternating the measurement, manually moving between the two points. although made by hand, are quite faithful in the average dimensions measured, so they represent an important yardstick for establishing the conditions of use. On the other hand, the use of impact-time data permits to overcome these limitations, and these two types of measurement can be integrated to obtain the real state of detachments of the object, as it was demonstrated in Figure 12.  
Finally, in Figure 10 we show a measurement made on a sample of real mosaic (flooring of Roman origin, coming from the archaeological area of Tivoli, Roma) measuring 20 \(\times\) 20 cm. This mosaic comes from a restoration carried out in the 1970s, and applied using cementitious material to a tile used as a base. Over the years, unfortunately, the upper left corner has undergone a partial detachment from the base. In this case the detachment is evident and the measurement carried out was intended to confirm the naked eye analysis. The discovery of a further detached and invisible area was of great impact to the experts to whom the verification of the measure was subjected.