# Computer Vision-Based Approach for Reading Analog Multimeter
## 5 Results and Discussions
### Experimental Results on Linear Cases  
In order to test the feasibility of our method under different rotations (\(rotation_{A-meter}\)) and illuminations (mean intensity \(\bar{I}\)) of the A-meter YF-370A, five measurements for each scenario were performed by human eyes and the proposed approach and were analysed and compared. We checked the function select (\(FS_{h}\)) detected and the read value (\(V_{h}\)) obtained by human eyes and those (\(FS_{p}\) and \(V_{p}\)) by the proposed method, respectively and then evaluated the accuracy with Equation (24). Note here that if the signs of \(rotation_{A-meter}\) were positive, it meant that the A-meter was rotated to the left; otherwise it was rotated to the right. In addition, the lower the \(\bar{I}\) was, the darker the illumination was, and vice versa. The first scenario (1) was to let function select be \"OFF\", where the measurement resulted in 100% accuracy, as reported in Table 4. This means that the rotated A-meter was horizontally adjusted, and the function select and the meter pointer were detected correctly for each case by the proposed method. Note here that since both \(V_{h}\) and \(V_{p}\) were 0, they were identical and Equation (24) was not needed. For scenario (2), the A-meter was set to function \"ACV 250\" to measure the 110 Vac line power. Table 5 reports the mean accuracy as 97.28%. Note here that the second row is a slightly tilted case with low illumination, as shown in Figure 14. In this tilted example, \(\theta_{s}=40.827^{\circ}\in[27^{\circ},45^{\circ})\) represents that the function \"ACV 250\" was selected and \(A(\theta_{s})=250\) was used according to Equation (1) and Table 1, where \(F(\theta_{s})=2\) implies that this example is a linear case. In addition, \(\theta_{r}=45^{\circ}\), \(\theta_{l}=134.393^{\circ}\) were obtained respectively by Equations (16) and (17) using the detected \(\textbf{R}_{\textit{right-end}}\) and \(\textbf{R}_{\textit{left-end}}\), as detected in Figure 14c. Through our scanning process (using \(\Delta\theta=0.12\)) on the \(GA\)-profile as shown in Figure 14b, \(\theta_{p}=95.974\) was thus detected. Since the current example is a linear case, Equation (3) was used and the read result \(V_{p}=107.444\) Vac was finally obtained. Even the A-meter was rotated \(15.947^{\circ}\) and the illumination was low: \(\bar{I}=49.8\). In this case, the result \(V_{p}=107.444\) Vac obtained by the proposed method is very close to the \(V_{h}=108\) Vac observed by human eyes. Table 6 reports the results for scenario (3), where the function \"ACV 250\" was also selected to measure the 220 Vac line power. The mean accuracy was 98.86% except for the fifth data point, since it was difficult to read by the human eye (but our system read the value as 236.450 Vac) under very low illumination (\(\bar{I}=7.5\)). The results of the other linear cases (scenarios (4)-(10)) using function selects of \"DCV 2.5\", \"DCV 10\", \"DCV 50\" as well as \"DCmA 25\" are reported in Table 7. From these experimental results, it is shown that all of the function selects were detected with 100% accuracy. The pointer was detected very accurately and the mean accuracy of the reading value for most of cases was 95% or above. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \(Rotation_{\textbf{A-meter}}\) & \(\bar{I}\) & \(FS_{h}\) & \(V_{h}\)(Vac) & \(FS_{p}\) & \(V_{p}\)(Vac) & _Accuracy (\%)_ \\ \hline \(-1.245^{\circ}\) & 124.7 & ACV 250 & 225 & ACV 250 & 229.775 & 97.88\% \\ \(11.303^{\circ}\) & 55.6 & ACV 250 & 225 & ACV 250 & 225.682 & 99.70\% \\ \(29.985^{\circ}\) & 73.2 & ACV 250 & 224 & ACV 250 & 223.604 & 99.82\% \\ \(-17.144^{\circ}\) & 61.5 & ACV 250 & 225 & ACV 250 & 229.434 & 98.03\% \\ \(-21.066^{\circ}\) & 7.5 & Difficult to read & ACV 250 & 236.450 & NA \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Results of using A-meter YF-370A with function select “ACV 250” to measure the 220 Vac line power.