## 5 Results and Discussion  
### Preparatory Works  
Test and measurement equipment must undergo a calibration process with respect to standard equipment before being used. This calibration process makes it possible to characterize the equipment in terms of the precision and accuracy of the measurements it produces. Test and measurement equipment will be valid to perform the desired measurement if the precision and accuracy values meet the requirements of the intended application. It is possible to have a device that produces measurements with a high dispersion of values but which are within the admissible margins for the desired application, in which case it will be a feasible device. Conversely, it is also possible to have a measuring device with high precision and accuracy, but insufficient for the specific target application. All quantities measured in structural testing of aircraft components are measured by means of properly calibrated equipment. The calibration process consists of taking a series of measurements of values within the range of interest, repeating those measurements several times, and comparing them with the values produced by a standard measuring equipment, whose calibration status is accurately known and adjusted to the requirements of the test. The value resulting from the calibration is the measurement uncertainty of that equipment, which defines the range of true values within which the measurements produced by the calibrated equipment lie. There are different methods for calculating measurement uncertainty. The approach employed in this study, one of the most common, is the expanded uncertainty with a zero correction, calculated by the expression  
\[U=k\cdot u \tag{1}\]  
where \(U\) is the global expanded uncertainty with null correction, \(k\) is the coverage factor that takes the value 2 for a coverage of 95%, and \(u\) is the global standard uncertainty with null correction, which is calculated by the expression  
\[u=\sqrt{(u_{CG})^{2}+(u_{CR})^{2}} \tag{2}\]  
with \(u_{CG}\) being the global correction uncertainty and \(u_{CR}\) the residual correction uncertainty, which take into account the deviations between the measurements made by the equipment to be calibrated and the standard equipment, the uncertainties due to the repeatability and resolution of the measurements, and also the uncertainty of the standard equipment itself. In order to adequately evaluate the viability of the proposed architecture for aeronautical structural tests, not only must the criteria of the wireless network and data transfer be taken into account, but also the requirements of precision and accuracy of measurement of the sensors used must be met. Therefore, the sensors used in this study were subjected to calibration processes prior to their use in tests. For each of the sensors, three series of up to six different measurements of values within the admissible range were taken and compared with standard equipment. As a result, the uncertainty values for each sensor were 0.76 \({}^{\circ}\)C for the temperature sensor, 0.39\({}^{\circ}\) for the inclination sensor and 5.41 mm for the position sensor. It was found that these uncertainty values were very similar to those of the conventional measuring equipment used in the test. Figure 9a shows the values of the measurements taken with the position sensor during the calibration process. It is observed that the high accuracy of the measurements was taken with a small variation between the three different measurements made in each of the six positions. It can be seen that the error of the measurements produced by the sensor has a quadratic tendency, and that for the calibration range, its value is lower for more distant positions and higher for lower position values. The temperature sensor produced the calibration values shown in Figure 9b. It can be seen in this graphic that the sensor has a high accuracy and a very controlled measurement dispersion. The trend of the measurement error is quadratic with a high curvature that gives it an almost linear character.