A new experimental device dedicated to the experimental studies of wildland fires is proposed. It uses two Medthermreg heat flux sensors and a thermocouple fixed on an insulated support. The whole sensors are connected to a data logger buried under the ground surface, which avoid the use of long connection cables all over the field. This device can perform accurate measurements of high heat fluxes thanks to water- cooled sensors. This new experimental device was made to resist to intense heat emitted from large spreading fire fronts. The temperature of the sensors is checked during fire spread. One experimental fire spread across dead shrubs composed of oak branches was performed. The designed heat sensor is used in combination with a two-dimensional anemometer and photographs. The results provided here illustrate both the efficiency of the sensors' insulation and cooling system and the relevancy of intrusive heat flux measurements. Some new insights about thermal balances from a real scale fire are suggested, in comparison with previous available data acknowledgements.