This system can appreciate the lowest modal frequency of the structures but not the highest due to the low sampling rate. In [17], instead, a single-node wired monitoring system is presented that can identify natural frequency and modal parameters in real time. The system is based on a single board computer which limits the synchronization and the maximum number of connected nodes in the same network. Finally, in [18] a system which acquires data if the event exceeds a certain threshold is presented, with an acquisition duration of 70 s.  
Even from the point of view of wired or non-wired systems, there is no solution objectively better than the other, but reference must be made to the particular needs involved. Speaking of strengths and weaknesses, undoubtedly the wired monitoring system generally has a very high cost, a typically low number of sensors that can be connected in the same network, high bandwidth, high data rate of the sensors and very high synchronicity of the sensors. On the other hand, the wireless monitoring system has low cost, a large number of sensors that can be connected in the same network, limited bandwidth, low sensor data rate, and critical node synchronization [19]. However, regardless of the particular characteristics of each of them, all the systems presented up to now are of the master multi-slave type where, practically, a central master unit communicates with several distributed slave units. In an accelerometer-based master multi-slave system, the master unit serves as the central processing hub responsible for managing multiple slave units distributed across the structure and collecting data from them through on-board accelerometers. Beyond SHM, master multi-slave accelerometer-based systems are used in several other fields [20; 21; 22], proving their versatility. Among the traditional methods for SHM, modal harmonic analysis emerged as a powerful tool for this field, enabling the extraction of valuable information about the dynamic behavior and static status of structures [23; 24]. These kinds of data are extracted by changes in natural frequencies, mode shapes and damping ratios of the structure in function of a determined excitation, which could be controlled or natural, e.g., mechanical stimuli or environmental excitation. Dynamic responses, which makes it possible to extract the aforementioned data through several algorithms [25], are retrieved by a system composed of accelerometers, whose displacement gives information about the dynamic and static situation of the structure. In this paper, we propose a fully custom master multi-slave accelerometer-based system employed for SHM based on modal harmonic analysis. The aim of our research is to use a number of these devices in a meshed network to detect changes in the structure modal response after an artificially induced alteration. The paper is organized as follows: in the following section, the internal architecture of the system and its operating principle are discussed, while in Section 3, results extracted from several measurements involving time and frequency domains are reported. Finally, in Section 4, the feasibility of this method and conclusions are discussed, presenting several enhancement points for future implementations.