# Accuracy Characterization of a MEMS Accelerometer for Vibration Monitoring in a Rotating Framework
## 3 Results and Discussion
According to the presented outcomes, the proposed inexpensive vibration monitoring system may be deployed both in wind turbine and turbomachinery fan blades by positioning the accelerometer at a proper distance from the rotation axis. The power consumption of both the reference and MEMS-based wireless systems is another critical feature that should be compared. In fact, while the reference system includes benchtop instruments that require hundreds of watts, without considering the reference and MEMS-based wireless systems, the reference and MEMS-based wireless systems are compatible with the ones assessed with the reference monitoring system. According to the presented outcomes, the proposed inexpensive vibration monitoring system may be deployed both in wind turbine and turbomachinery fan blades by positioning the accelerometer at a proper distance from the rotation axis. The power consumption of both the reference and MEMS-based wireless systems is another critical feature that should be compared. In fact, while the reference system includes benchtop instruments that require hundreds of watts, without considering the reference and MEMS-based wireless systems, the reference and MEMS-based wireless systems are compatible with the ones assessed with the reference monitoring system. According to the presented outcomes, the proposed inexpensive vibration monitoring system may be deployed both in wind turbine and turbomachinery fan blades by positioning the accelerometer at a proper distance from the rotation axis. The power consumption of both the reference and MEMS-based wireless systems is another critical feature that should be compared. In fact, while the reference system includes benchtop instruments that require hundreds of watts, without considering the reference and MEMS-based wireless systems, the reference and MEMS-based wireless systems are compatible with the ones assessed with the reference monitoring system. the remote PC power consumption, the wireless system must be able to operate in a rotating framework, thereby a low power consumption is entailed. Table 4 summarizes the key characteristics of both setups in terms of power supply requirements. The wireless system power consumption was always lower than 6 W during the whole measurement campaign. This power demand can easily be met from small-size solar panels, as reported in Ref. [44], eliminating the need for a slip ring to supply the proposed device. Figure 5: FFT of the reference and MEMS accelerometer signals at a rotor speed of 300 rpm, considering: (**a**,**b**) the first resonant mode, (**c**,**d**) the second resonant mode, (**e**,**f**) the third resonant mode, and (**g**,**h**) the fourth resonant mode. The proposed vibration monitoring system appears to be capable of accurately detecting vibrations at a resonance within 2.4 kHz. This bandwidth is much wider than 1-150 Hz, which would be required to monitor the first nine resonances in axial wind turbine blades longer than 2.5 m [45]. Moreover, the MEMS-based system offers the remarkable advantage of real-time and remotely controllable monitoring. This is critical for the viability of the proposed device, since it is essential to accurately assess both frequencies and accelerations to evaluate whether the rotating structure is safely operating or the vibration level exceeds the warning threshold and activate, if present, an active control system. \begin{table}
\begin{tabular}{c c c} \hline
**Component** & **Voltage Range** & **Current** \\ \hline \multicolumn{3}{c}{**Reference System**} \\ \hline NI 6341 & 11 to 30 VDC & 1 A \\ PCB 482C & 100 to 240 VAC & \(\leq\)0.7 A \\ PCB 352A56 & 22 to 30 VDC & 2 to 20 mA \\ \hline \multicolumn{3}{c}{**Wireless System**} \\ \hline Raspberry PI 4 & 5 V & 3 A \\ MCC 118 & 3.3 V & 35 mA \\ ADXL356 & 2.5 V & 150 \(\mu\)A \\ \hline \end{tabular}
\end{table} 
Table 4: Main power supply requirements for each considered vibration monitoring system.