## 4 Results
### Ergonomics Assessment  
Once the prototype was functional, it was evaluated in terms of ergonomics. It is a science focused on equipment design with a human-centered approach to reduce operator fatigue or discomfort considering physical, cognitive, social, organizational, and environmental factors [38; 39]. Since this science focuses on improving design performance,  
Figure 14: Main PCB. Figure 15: Second PCB. the degree of usability must be quantified to accurately assess the ease of use of the designed prototype; therefore, several helpful methods exist for this purpose. For instance, keystroke-level model, link analysis, questionaries, checklist, hierarchical task analysis, layout analysis, and interview, among others [39]; the selection of the methods for the assessment depends on the project's design stage in this case. the project has a functional and physical prototype. Therefore, the methods selected were observation for the usability link analysis and layout analysis for the ergonomics test [39]. The observation method was performed by giving the users the device and asking them to perform planned activities; in this case, six users were selected, and six different activities were established:  
1. Move the station to a specific point. 2. Turn on the device. 3. Set the measurement interval time to 24 h.
4. Turn off the display. 5. Open the case to get access to the internal components. 6. Remove the SD card. Only six users were selected since, when evaluating the usability of a product, it is enough for only five users to use the product because they will find more than 75% of the product issues. Using fewer users will lead to not covering most of these problems; meanwhile, using more than six users, repeated issues will be found, making the results meaningless [40]. Each user had ten points at the beginning of the test, and then each wrong action or asking of a question was penalized by subtracting one point each time; in addition, the time that the user took to complete all the activities was measured. Table 5 shows the average score of each activity performed by the six users and the average time. In general, the overall score was 8.7 regarding usability. Regarding ergonomics, the layout and link analyses were performed simultaneously on the human-machine interface presented in Figure 12. The first method states that the components from the same category must be as close as possible. There were only two categories found: device control and power. On the other hand, the second method consists of establishing a sequence of actions that would be one of the most common sequences while using the device in a normal operational mode and tracing lines between the components following that order [39]. In this case, the sequence was:  
1. Turn on the device. 2. Check the indicator LEDs. 3. Turn on the display. 4. Watch the display and the measurements. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Activity** & **Score Average** & **Average Time** \\ \hline Move the station to a & & \\ specific point & 9.5 & \\ \hline Turn on the device & 9.5 & \\ \hline Set the measurement interval & 9 & \\ time to 24 h & & 4:14 min \\ \hline Turn off the display & 8.8 & \\ \hline Open the case to get access to & & \\ the internal components & 8.6 & \\ \hline Remove the SD card & 6.7 & \\ \hline Average & 8.7 & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Observation method results for the usability test. Change the measuring interval time to a different value. Figure 16 depicts the two groups (red for device control and blue for power) and the lines (green) that follow the order established. The device control group includes the components labeled B, C, D, and E; the power group includes only component A. Once the lines are traced, the method establishes that no line should cross with another to enhance operability and ergonomics. In this case, line A-E crosses line C-D, indicating that one or more components should be relocated.