# Computer Vision-Based Approach for Reading Analog Multimeter
## 5 Results and Discussions
### Further Results and Discussion
\begin{table}
\begin{tabular}{c c c} \hline _Scenario_ & _Mean Measured Value_ (Vdc) & _Mean Accuracy_ (\(\%\)) \\ \hline (1) Shifted right & 24.388 & 98.38\% \\ (2) Rotated right & 24.260 & 98.80\% \\ (3) Shifted right and rotated left & 24.432 & 98.19\% \\ (4) Shifted left & 23.538 & 97.97\% \\ (5) Rotated left & 23.455 & 97.73\% \\ (6) Shifted left and rotated right & 23.719 & 98.83\% \\ \hline \end{tabular}
\end{table} 
Table 11: Statistical results of the measured DC voltages plotted in Figure 19.  
Figure 16: (a) Rotating the camera left will make the A-meter in the captured image rotate to the right. (b) Rotating the camera right will make the A-meter in the captured image rotate to the left. Figure 17: An illustrative result directly displayed on the LabVIEW environment for scenario (2), “A-meter rotated right” (24.639\({}^{\circ}\)), presented in Section 5.3. Figure 19: Plots of the measured DC voltages by our computer vision-based approach for reading the A-meter with different translations and/or rotations. The ground truth was 24 Vdc (the DC voltage), as provided by a tester calibrator (model AOIP CMU 310). Figure 18: An illustrative result directly displayed on the LabVIEW environment for scenario (5), “A-meter rotated left” (23.484\({}^{\circ}\)), presented in Section 5.3. Currently, the proposed algorithms are implemented in the LabVIEW environment [19] by combining with the C codes and plotting the visualized results for functional verification only. The execution time still bounds in the \"second\" level with an image size of \(2304\times 1536\) pixels for processing. Most of the time is spent on template matching and horizontal alignment. It takes about 90% of the whole execution time in the current implementation. The time taken to detect the pointer and read the value takes around 1 sec, as the videos demonstrate in reference [22; 23]. The first video [22] shows the stability of locating the \(\mathbf{R}_{right-end}\) and the \(\mathbf{R}_{left-end}\in\mathbf{R}_{IM}\) and reading the value. The second video [23] demonstrates the scanning process to detect the pointer and read the value. Based on the effectiveness of reading the A-meter with the presented method, an application to read the dials attached on a liquid nitrogen tank is further demonstrated in the next section. As a result, the computer vision-based approach has been proposed to effectively read the value on not only the linear scale but also on the nonlinear scale indicated by the pointer from an analog multimeter. Through a comparison of the results obtained by the proposed method to those obtained by both human eyes and the digital multimeter, our experiments confirmed that the accuracy of locating the function select is 100%, and the mean accuracy of reading the value from the A-meter \begin{table}
\begin{tabular}{c c c} \hline \hline _Camera Location_ & _Mean Measured Value (Vdc)_ & _Mean Accuracy_ (\%) \\ \hline B & 23.960 & 99.14\% \\ C & 23.811 & 98.98\% \\ D & 23.807 & 99.09\% \\ E & 23.598 & 95.81\% \\ F & 23.706 & 98.32\% \\ G & 23.447 & 97.19\% \\ \hline \hline \end{tabular}
\end{table} 
Table 12: Statistical results for the camera located at B, C, D, E, F, and G of the effective range drawn in Figure 20.  
Figure 20: The effective range to place the camera in to read the A-meter is roughly confined within the zone bounded by the edges among B-C-D-E-F-G-B. If the camera is placed outside this region (e.g., H and I), the reading of the A-meter will fail. is 95% or above,except for some cases affected by the _little-change-large-multiplier effect_. Our method was also shown to perform well under situations where the A-meter is rotated, slightly tilted, and/or illumination varied and thus, its feasibility and effectiveness are confirmed.