https://www.futureelectronics.com/resources/featured-products/melexis-mlx90632-infrared-temperature-sensor . Melexis MLX90632 infrared sensor is based on established far infrared (FIR) technology that utilizes the fact that every object emits heat radiation proportional to its temperature. The ultra-small device includes the sensor element, signal processing, digital interface and optics allowing integration into a wide variety of space-constrained applications. 
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