## 3 Results and Analysis of Radiometric Thermal Data
### Analysis of Measurement Result Deviations  
There are two basic approaches to analyzing thermographic records. One is to determine the highest temperature that the object under study can withstand. In our case, we were dealing with temperatures as high as 90 \({}^{\circ}\)C, which most structural- and electrical-insulating materials must withstand for a short period of time. The second approach is to determine the temperature difference between two identical objects, i.e., between a correct and an incorrect one, and to decide, based on the magnitude of the temperature difference, which method and time interval should be used to respond to the observed anomaly. It should always be kept in mind that an infrared thermal imager does not measure temperature but registers radiation. The deviation of the calibration data from the reference temperature represents an indication of correctness if all recording parameters have been entered correctly. Table 6 shows the deviations in \({}^{\circ}\)C and has been expanded to include information on average camera prices so that the accuracy data can be correlated with financial indicators. \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline \multirow{2}{*}{**Device**} & \multicolumn{6}{c}{**Average Measurements for Defined Reference Points (\({}^{\circ}\)C)**} \\ \cline{2-7}  & **27** & **30** & **33** & **36** & **39** & **42** & **45** \\ \hline Flir E6 & 29.03 & 32.13 & 35.20 & 38.05 & 41.25 & 44.50 & 45.70 \\ Flir E60 bx & 27.77 & 30.85 & 33.85 & 36.93 & 39.95 & 43.05 & 45.90 \\ Flir One Pro & 27.52 & 26.63 & 29.40 & 30.08 & 32.50 & 36.10 & 37.50 \\ Flir A500 & 27.07 & 29.73 & 32.74 & 35.92 & 38.64 & 41.89 & 44.68 \\ Flir A70 29\({}^{\circ}\) & 22.03 & 24.09 & 27.87 & 29.27 & 31.55 & 34.76 & 37.22 \\ Flir A70 95\({}^{\circ}\) & 26.50 & 29.76 & 32.97 & 36.27 & 39.32 & 42.42 & 46.10 \\ HTI HT-301 & 27.64 & 29.67 & 35.18 & 37.01 & 41.72 & 42.53 & 45.73 \\ Raytek RAYMX2D & 27.57 & 30.53 & 33.65 & 36.72 & 39.65 & 42.61 & 45.69 \\ Parkside PTIA 1 & 26.91 & 29.44 & 30.84 & 34.55 & 37.31 & 39.12 & 39.69 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Temperature readings during the calibration process. Figure 23: The maximum camera distance up to which accurate measurement is possible. If the mean value of the deviation for the individual devices is plotted, a comparison can be made with the data from Table 3. From Figure 24, it is clear that the Flir A70 (Teledyne FLIR LLC, Wilsonville, Oregon, USA) with a lens angle of 29\({}^{\circ}\) was not correctly factory calibrated and it is not suitable for further use. The Flir One Pro showed a deviation from the nominal accuracy of 34%, but considering the price and the purpose, which is primarily qualitative, we cannot consider it to be deficient. When the data from Table 6 were put into a graphical form, as shown in Figure 25, it was possible to clearly distinguish the cameras that were accurate and precise in terms of accuracy over the entire temperature range of the calibration. Going one step further and analyzing the percent deviation from the mean of the deviation for each temperature, as shown in Figure 26, can lead to a false conclusion, as the most accurate camera showed an increase in deviation as the temperature increased. The