# An OCARI-Based Wireless Sensor Network for Heat Measurements during Outdoor Fire Experiments
## 3 Experimental Protocol
### Experimental Plot  
In configurations 1 and 2 (Figures 6 and 7), we conducted three large-scale fire experiments. Specifically, 10 m\({}^{2}\) of fuel bed was formed by spreading excelsior with a 2 to 8 kg/m\({}^{2}\) fuel load from a height ranging from 50 to 90 cm, and this resulted in flames with heights ranging from 1 to 4 m. Facing the flame front, a set of transducers is displayed by a couple (i.e., two thermocouples or two radiative heat fluxes), and each element of a couple is plugged on a wireless node or its  
Figure 5: Heat sensor interface for an OCARI node. wired counterpart, namely the CR 3000 Campbell Scientific. The main experiments characteristics are reported in Table 1. The horizontal wind speeds are recorded using a 2D ultrasonic anemometer sampled at 1 Hz. Two configurations were selected to monitor the fire, namely a vertical monitoring of the horizontal component of heat radiation (i.e., parallel-to-the-ground, C1, Figure 6) and horizontal \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Experiment** & **Fuel Load** & **Wind Direction** & **Wind Speed** \\ \hline Experiment C1 1 & 2 kg/m\({}^{2}\) & Flow opposed to the sensing & 3 m.s\({}^{-1}\) \\ Experiment C1 2 & 4 kg/m\({}^{2}\) & No wind & \textless{} 0.5 m.s\({}^{-1}\) \\ Experiment C1 3 & 8 kg/m\({}^{2}\) & Flow towards the sensing & 8 m.s\({}^{-1}\) \\ Experiment C2 1 & 2 kg/m\({}^{2}\) & Flow towards the sensing area & 3.5 m.s\({}^{-1}\) \\ Experiment C2 2 & 4 kg/m\({}^{2}\) & Flow towards the sensing area & 4 m.s\({}^{-1}\) \\ Experiment C2 3 & 8 kg/m\({}^{2}\) & Flow towards the sensing area & 2.4 m.s\({}^{-1}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Large-scale fire experiment settings in configurations C1 and C2. Figure 6: Experimental protocol for large-scale fire test in configuration C1: The 8 kg.m\({}^{2}\) case is presented (**top**). Configuration 1 differs from configuration 2 with respect to the position of measurement points in the axis of the plot and the nature of the measurement points. Specifically, the aim of C1 involves displaying central HMFs in a vertical direction, whereas C2 sets them in a horizontal direction. In the C1 configuration (Figure 6), sensors are located at a height of 0.5 m above the ground for nodes 2, 3, and 4, while node 1 is at a height of 1.5 m from the soil. Specifically, C1 evaluates the heat radiation that impacts a vertical axis at a distance of 3.3 m from the left edge of the plot (Figure 6). Additionally, C2 investigates the penetration of the heat radiation along the central axis of the plot (Figure 7), and each sensor is located at a height of 0.5 m. Sensors 2 and 4 are separated by a distance of 1 m in the C2 configuration. Furthermore, another difference exists in temperature measurements between both configurations. Specifically, C1 leads to a single temperature measurement at the centre of the vegetal plot (N5 in C1), while C2 leads to two temperature measurements along the central axis of the plot (N2 and N4 in C2). Each node is identified by an integer corresponding to 1, 2, 3, or 4 on the experimental WSN, as reported in Table 2 (respectively, Table 3) for the C1 configuration (respectively, C2). The wired and wireless thermocouples are separated by a distance of less than 0.5 cm, thereby allowing the assumption that they measure the same local temperature. The aim of the present study also involves observing the effects of HFM sensitivity when implemented on the OCARI-based WSN. Thus, two sensitivities of the HFM were used for the comparison of the wireless system with the wired system as follows: 20 kWm\({}^{2}\) (N3 and N4) and 200 kWm\({}^{2}\) for embedded measurement points (N5 and N7). In configuration 2, nodes N1 and N2 are connected to 20 kWm\({}^{2}\) HFMs (referring to LHFL data on plots), whereas nodes N3 and N4 are plugged with 200 kWm\({}^{2}\) (referring to HHFL data on plots). Please note that these experiments did not involve a large spanned wireless network, which is the aim of an operational WSN.