# An OCARI-Based Wireless Sensor Network for Heat Measurements during Outdoor Fire Experiments
## 3 Experimental Protocol
### Heat Measurement Devices  
Heat data are collected with standard thermocouples and radiative heat fluxmeters (HFMs) that are typically used for fire experiments [1; 2; 3; 22; 23; 24]. We performed two types of heat measurements as follows:  
* _Measurement of gas temperature_ (in both air and fuel beds): Gas temperature \(T\) is measured around the transducer and makes it possible to detect the presence of smoke (60 \({}^{\circ}\)C \(<\) T \(<\) 500 \({}^{\circ}\)C) or flame (500 \({}^{\circ}\)C \(<\) T ) as per fire safety engineering standards;* _Measurement of radiant heat fluxes_: The system measures heat radiation from the fire to the target sensor.  
The measurement of the gas phase temperature is performed with a K-type thermocouple that corresponds to a transducer that obeys the thermoelectric effect or Seebeck effect. This effect is due to a junction (hot weld) of two electrical wires wherein each is composed of a different alloy at \(T_{1}\) temperature. A second junction (cold weld) is at \(T_{2}\) reference temperature. The temperature difference between the hot and cold junctions is converted into an electric potential difference or voltage in which temperature exhibits a linear behaviour.  
Temperatures are measured using chromel-alumel type thermocouples (K-type) that are sensitive in the \(-100\)\({}^{\circ}\)C to 1370 \({}^{\circ}\)C measurement range. The thermocouples exhibit a 250 \(\upmu\)m diameter gained junction with a response time of 0.3 s. They are connected to an amplifier module (\(+/-40\) mV for voltage output of the transducer) and allow a full-range temperature measurement capable of facing a large-scale fire of vegetal fuel.  
The radiant heat flux measurement is performed via Medtherm (c) heat fluxmeters (HFM). The HFM relies on temperature measurements on the hot and cold sides of a cylindrical shape solid where the hot side is exposed to the heat flux. The incident radiant heat flux is obtained from the measured heat flow passing through the solid on the exposed side. The heat flux sensor calibration lies primarily with an exposure to a reference flux emitted by a black body at a high temperature and the radiative source based upon [PERSON]'s radiation law. In the present experiment, we used two models of HFMs: The first obtained 0-20 kW/m\({}^{2}\) as the maximum level of heat radiation, and the second obtained 0-200 kW/m\({}^{2}\).  
All Medtherm heat fluxmeters are manufactured with a measurement error corresponding to 3% of the responsivity, with a coverage factor corresponding to 2 for a 95% confidence interval based on the Medtherm black body calibration report for two measuring ranges (0-20) (Schmidt-Boetler gauge) and 0-200 kW/m\({}^{2}\) (Gardon gauge). For example, a domestic oven emits approximately 5 kW/m\({}^{2}\) at full power. The Medtherm HFMs produce a signal between 0 and 10 mV, and this is in accordance with the analogue inputs of the OCARI's data acquisition cards constructed for the OCARI's nodes. Calibration is set according to the ISO9014 standard for heat measurements in fire engineering [25].  
This difference in HFM sensitivity is noted as LHFL for the 0-20 kW/m\({}^{2}\) range (low-heat flux level) and HHFL for the 0-200 kW/m\({}^{2}\) range (high heat flux level). With respect to a given fire in the open, the HFMs typically present a slight difference when plugged on the standard wired datalogger used here. The study involves examining the effect of the difference in sensitivity when used with the OCARI wireless system.