# Mitigation of Electro Magnetic Interference by Using C-Shaped Composite Cylindrical Device
## 3 Results and Discussion
### Monitoring of Electromagnetic Fields  
The cases of the C-shape high-permeability material and the permalloy material were set to confirm that whether the opening direction of the C-shaped cylindrical device interfered with the measured electromagnetic fields. Several voltages at a frequency of 60 Hz were applied in the coils, and the electromagnetic background was 0.3 mG. The peak values were recorded for the tubular structure, the vertical (i.e., the Y-axis) opening, and the horizontal (i.e., the X-axis) opening on the high-permeability material. The detailed experimental results are listed in Table 2. It is noted that the opening in the horizontal direction of the high-permeability material shielded electromagnetic fields above 1 dB. The opening in the vertical direction of the high-permeability material shielded the electromagnetic field below 1 dB, because of the collinear with the C-shaped opening. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Distance (D; cm)**} & \multicolumn{2}{c}{**Electromagnetic Field (nT)**} \\ \cline{2-4}  & **Tubular Structure (T)** &
\begin{tabular}{c} **C-shape Composite** \\ **Device (C)** \\ \end{tabular} & **Efficiency (dB)** \\ \hline \(-\)100 & 186 & 170 & \(-\)0.78 \\ \hline \(-\)90 & 188 & 172 & \(-\)0.77 \\ \hline \(-\)80 & 199 & 181 & \(-\)0.82 \\ \hline \(-\)70 & 217 & 196 & \(-\)0.88 \\ \hline \(-\)60 & 245 & 221 & \(-\)0.90 \\ \hline \(-\)50 & 288 & 256 & \(-\)1.02 \\ \hline \(-\)40 & 358 & 311 & \(-\)1.22 \\ \hline \(-\)30 & 471 & 397 & \(-\)1.48 \\ \hline \(-\)20 & 697 & 551 & \(-\)2.04 \\ \hline \(-\)10 & 1424 & 855 & \(-\)4.43 \\ \hline \(10\) & 1483 & 2022 & 2.69 \\ \hline \(20\) & 701 & 879 & 1.97 \\ \hline \(30\) & 473 & 557 & 1.42 \\ \hline \(40\) & 357 & 405 & 1.10 \\ \hline \(50\) & 287 & 322 & 1.00 \\ \hline \(60\) & 245 & 271 & 0.88 \\ \hline \(70\) & 216 & 238 & 0.84 \\ \hline \(80\) & 199 & 217 & 0.75 \\ \hline \(90\) & 189 & 206 & 0.75 \\ \hline \(100\) & 185 & 202 & 0.76 \\ \hline \end{tabular}
\end{table} 
Table 1: Simulation data of electromagnetic fields. Figures 3a-b and 4 demonstrate the comparison of the measured electromagnetic fields from the tubular structure without an opening and the C-shaped cylindrical devices with an opening in the Y-axis (top) and an opening in the X-axis (right). The results suggested that the emission of electromagnetic fields could be directive according to the C-shaped opening position. Further, the high-permeability material and the permalloy material were used to confirm the shielding efficiency of the C-shaped cylindrical device. The electric current coil was wrapped into the center of the tubular permalloy structure and its corresponding C-shaped cylindrical device. A voltage of 1.43 V with a current of 0.6 A at a frequency of 60 Hz was applied in the coil, while the electromagnetic background was 0.3 mG. The peak value was recorded for the horizontal opening on the permalloy pipe. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Voltage** **(V)**} & \multirow{2}{*}{**Current** **(A)**} & \multirow{2}{*}{**Tubular** **Structure** **(T) in nT**} & \multicolumn{2}{c}{**C Opening (C) in nT**} & \multicolumn{2}{c}{**Efficiency (dB)**} \\ \cline{4-7}  & & & **Structure** **(T) in nT** & **In the X-axis** & **In the Y-axis** & **In the X-axis** & **In the Y-axis** \\ \hline
2.5 & 0.39 & 904 & 805 & 842 & \(-\)1.01 & \(-\)0.62 \\ \hline
2.0 & 0.31 & 730 & 640 & 670 & \(-\)1.14 & \(-\)0.74 \\ \hline
1.5 & 0.22 & 526 & 430 & 501 & \(-\)1.75 & \(-\)0.42 \\ \hline
1.0 & 0.15 & 379 & 337 & 353 & \(-\)1.02 & \(-\)0.62 \\ \hline
0.5 & 0.07 & 194 & 171 & 179 & \(-\)1.10 & \(-\)0.70 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Results of electromagnetic fields (peak value) in the C-shaped high-permeability material. Figure 3: Setups with a C-shaped opening along the X-axis and Y-axis separately.