## 3 Experimental Results and Discussion
### HMI Dashboard  
Figure 10 shows the appearance of the main menu display used for real-time plant monitoring. It consists of three main monitoring parts:  
1. The left part shows air monitoring. 2. The center part shows leaf temperature monitoring. 3. The right part shows soil monitoring. Figure 9: Thermal camera alignment for (**a**) Plant-1 and (**b**) Plant-2. The air monitoring part displays the air temperature and humidity measured by the DHT22 sensor. These parameters are shown in the numerical display and animated gauge for easy monitoring. The leaf temperature and soil monitoring parts show the monitoring parameters of Plant-1 and Plant-2. The leaf temperature monitoring part consists of the thermal image visualization and the numerical displays of the leaf and background temperature. Our main contribution is the visualization of the thermal image that does not use standard image transmission. Instead, a Modbus TCP is employed to transmit 64 pixels of the thermal camera. In the Haiwell Cloud SCADA software, the 64 pixels (8 \(\times\) 8 pixels) are visualized using the image components, whose colors change according to the particular state. The state represents the temperature, where the number of states is limited to only twenty states (colors) for practical programming. The temperature value ranges from 20 to 40 \({}^{\circ}\)C and is visualized using purple to yellow colors, as shown in Figure 10. The thermal images in Figure 10 show that the leaf areas denoted in Figure 9 appear greenish, while the background is yellowish. This indicates that the leaf temperature is warmer than the background. The calculated leaf and background temperatures are shown on the right sides of the thermal images in Figure 10. Plant-1's leaf and background temperatures are 33.1 and 37.1 \({}^{\circ}\)C, respectively. Plant-2's leaf and background temperatures are 31.0 and 36.4 \({}^{\circ}\)C, respectively. The temperature value for all 8 \(\times\) 8 pixels of each thermal camera is shown in Figure 11, which appears when a \"Camera Data\" button in the main menu is pressed. The temperature values shown in Figure 11 are the values at the same time as shown in the display in Figure 10. Figure 11 can be used to check and debug the developed HMI program for visualizing the thermal image in Figure 10. Furthermore, Figure 11 helps us determine the plants' temperature profile under monitoring. Displayed in the soil monitoring part are the soil parameters (pH, temperature, moisture, EC, and NPK) measured by the JXCT sensor. Plant-1 and Plant-2 soil parameters are displayed on one screen for easy monitoring and comparison. All parameters (air, leaf temperature, soil), including the thermal images in the main menu, are updated every five seconds, which conforms to the execution time in the Raspberry Pi Zero W for processing the sensors. This time interval is fast enough for a real-time plant monitoring system. Figure 10: Main menu display. The other useful features of HMI are historical trend and data. The historical trend consists of eight displays:  
1. Historical trend of soil pH. It displays the trends in soil pH of Plant-1 and Plant-2. 2. Historical trend of soil moisture. It displays the trends in soil moisture of Plant-1 and Plant-2. 3. Historical trend of soil temperature. It displays the trends in soil temperature of Plant-1 and Plant-2. 4. Historical trend of soil electrical conductivity (EC). It displays the trends in soil EC of Plant-1 and Plant-2. 5. Historical trend of soil nitrogen. It displays the trends in soil nitrogen of Plant-1 and Plant-2. 6. Historical trend of soil phosphorous. It displays the trends in soil phosphorous of Plant-1 and Plant-2. 7. Historical trend of soil potassium. It displays the trends in soil potassium of Plant-1 and Plant-2. 8. Historical trend of air and leaf temperature. It displays the trends in air temperature, and leaf and background temperatures of Plant-1 and Plant-2.