Assessment of thermal drift of the FLIR A325sc camera: limits and recommendations
Abstract
Thermal drift of infrared camera remains a major problem for the accuracy and for repeatability of radiometric measurements. To control thermal drift, we have developed a cold box to set the temperature of the FLIR A325sc camera housing. Error chart is proposed to estimate the optimal camera operating temperature as a function of the ambient temperature for which the thermal drift due to camera housing is correctly managed.
The efficacy of the thermal drift compensation is examined over the two ranges of the camera. In the range [-20; 120] °C, the camera can be considered as calibrated until 110°C. The use of cold box enhances both efficacy of thermal drift compensation and reduces non-repeatability of irradiance measurements. The range [0; 350] °C highlights two behaviors: for emitting temperature within [65-225] °C, the thermal drift compensation is made difficult because of the self-heating of the measurement chain due to intensity of the black body irradiance. Above 225°C the optic considerably screens the irradiance and the compensation takes over. However, it is not enough to counteract the self-heating of the lens becoming more absorbent. A correction of thermosignal is proposed. The study is applyable to any of infrared camera