Calibration Technique for Heat Flux Sensors Used in Fire Experiments and Standard Fire Tests

A means of calibrating total heat flux gauges using a comparative (substitution) technique has been established. An apparatus consisting of a reference radiometer, a stable infrared radiant heater capable of producing flux levels up to 3.7 W/cm2, and a precision alignment mechanism has been constructed. The reference radiometer was characterized by the Radiometric Physics Division of the National Institute of Standards and Technology at flux levels in the range of 0.8 mW/cm2 to 0.9 W/cm2. Its accuracy was found to be within 3 percent over this range which spans 3 orders of magnitude. As the radiometer is a highly linear thermocouple-based device having a self-calibration feature, this accuracy is expected to hold up to 4.2 W/cm2, the upper limit of this device. Although the overall accuracy of calibrations performed in the new apparatus must still be established, it is expected to be within 3 to 5 percent.