The velocity of sound in air is temperature dependent. The higher the temperature, the higher the velocity of sound. While the sensor is designed to compensate for gradual changes in temperature, acute ambient temperature changes can adversely affect the sensor’s performance. This includes causing a sudden shift in the sensing window. If a hot object is to be detected, experiment by positioning the sensor so it is aimed at a cooler portion of the object. Also make sure the sensor is not sensing through hot air currents generated by the object as illustrated below.