## 6 Systems Encapsulation and Installation  
In the harsh environment of agricultural domain, the WSAN nodes' housings, as well as the total mechanical structure of them, is a key factor for the total robustness and reliability of the remote WSAN system [14]. The external influences that a WSAN node may suffer in an agricultural field may include chemical influences (such as acids, etc. ), dust, ice, corrosion, air moisture, aggressive constituents of rainwater (such as heavy metals, etc. ), solar radiation (UV radiation and high temperature), soil salinity, contamination from birds and insects, contamination from micro-organisms (such as fungi, moss, etc. ), and other factors related to air pollution. In order to protect the electronic circuits of the WSAN system from these external influences, particular enclosures proper for electrical and electronics systems are extensively used by both the commercial systems' vendors and the researchers. These cases are graded according to their resilience to dust and water (IEC IP Codes) [156]. In practice, these enclosures are the only solution for water ingress protection at outdoor deployments, but they are quite expensive and they are not so convenient in terms of the interior configuration of the electronics circuits and other electrical parts, such as batteries etc. Figure 26 shows a typical experimental configuration of a WSAN node for an agricultural application. In cases where a WSAN node requires a significant amount of energy autonomy, then more than one, or battery cells have to be used on the spot, installed in multiple electrical enclosures at the expense of cost, cabling distribution order, and appearance. Additionally, these enclosures suffer from drilling and cutting, which are frequent functions in experiments, and extra care has to be taken in order to maintain their durability against dust and water. Another issue is the support of the enclosures on the metallic support poles. Figure 27 shows a typical WSAN node implementation with a solar panel, a water-proof electrical enclosure and a metallic pole. In addition, significant complexity is usually added from the RF antennae installation because the antennae must be installed in such places where the electromagnetic signals are not influenced from the metallic materials of the WSAN node. This is the reason why the antennae are typically installed outside the enclosures or, in many cases, at additional support arms. Very often, all these issues are becoming sources for reduced reliability and durability for the deployed system. Figure 27: (**a**) An experimental WSAN node’s traditional enclosure installed at the back of a solar panel; (**b**) the front view of a typical WSAN node with its solar panel and its metallic support pole. Figure 26: (**a**) A typical electrical IP66-grade enclosure; (**b**) the internal configuration of a WSAN node’s electrical and electronic subsystems. Keeping all the aforementioned issues in mind, the use of ordinary drain and water supply tubes are proposed here as an extremely convenient solution for environmental and agricultural WSAN system enclosures. Tubes of polyvinyl chloride (PVC), or unplastisized polyvinyl chloride (PVC-U) inherently provide the required soil and dust ingress protection. According to the proposed SensoTube architecture, the various expansion shields are placed within a plastic tube (Figure 28). The PCB of the SensoTube board model has been designed so as to be fitted within tubes of 90 mm in diameter. The technical specifications of the PVC tubes are shown in Table 3. The selection of the pressure tolerance, e.g., 4 atms or 6 atms, influences the thickness of the tube. The very same tube acts also as the installation support pole. The height of the tube may vary according to the precise farming application needs. The WSAN system's boards can be placed at various heights within the tube. Developers can use tubes of smaller diameters under the boards' synthesis in order to act as a support spacer.