## 3 Materials and Methods
### Materials
#### 3.2.1 Hardware
The set of the company's products (assets) used for testing and experimenting with the RFID reading system is shown below, by applying RFID tags to all these products, in Figure 11. The tags were glued mainly and exclusively to the surfaces of the assets made of non-metallic materials (inserting them into the surfaces made of PVC plastic material). In addition, RFID tags were glued to small plastic bags with an asset inside in the case of two of the test elements. And, except for the aforementioned cases, a final label was applied directly to the metal (aluminium) surface of the respective product, in the total sample of assets to be tested, corresponding to a total of 15 sample pieces. As part of the above reasoning, one of the 15 pieces under study was then purposely labelled with an RFID tag glued to a metal surface to ascertain the real influence of this factor. Through the experiments to be carried out in the final phase, the intention was also to assess the possible additional interference of the metal surfaces of the products (especially those whose constitution was denser in metal, aluminium, or brass) on the good reading and identification of other tags (on other assets in the sample) that would be \"covered\" by the metal (in some of the pieces still with some thickness), overlapping between them and the antenna. In addition, other possible elements and sources that could affect the effective and correct identification and collection of information (from the EPC codes) on the test RFID tags were taken as initial hypotheses for the radio-frequency reading simulations. Finally, from a perspective less related to the problem under study, the case study company products that were used for the tests were mostly electro-pneumatic modules. This is still the type of product that constitutes the company's core business, with the highest sales volume. The two assets that remained in plastic bags correspond to items in which it was not possible to insert RFID tags to identify them on a non-metallic surface. These two assets correspond to objects made of aluminium on their entire surface. It is assumed that, for the type of traceability process to be explored, RFID tags (as with printed barcodes, which are also attached to the items themselves) should be placed directly on the objects or products that they will uniquely identify, and that this is the appropriate way to go about it. However, the fact that these labels were affixed in the way indicated above (on the bags) gave rise to a feature that also turned out to be useful for test results that were relevant to evaluating how RFID reading works. Many products that are waiting (for quality approval, and subsequent identification by the packaging operator and organisation into order boxes to be sent on to the customer) in the packaging section are actually in bags, so checking that the new system is always able to read the labels on the plastic bags correctly for the identification of these two test assets (by running simulations of passing through the system's reading field for a significant number of rounds) becomes crucial. All the 15 test assets, duly labelled, in a single, larger image are shown in Appendix A. Figure 12 shows a representation of the various test assets placed inside cardboard boxes for the company's product packaging, with different sizes, and with some being inside others in a specific way, considering the main phase of the experiment procedure that was carried out. Figure 11: Company assets that were used for the RFID tests. The purpose of this procedure was to simulate a common scenario of organising modules and other company products according to customer orders. This procedure is carried out in the packaging section, with careful attention on the part of the packaging operators to avoid as many errors as possible in the accounting of assets and, in parallel, in the grouping of products by orders and boxes for dispatch.