SR-18 UV Monitor
The SR-18 UV monitor was invented at the Smithsonian Environmental Research Center (SERC). A disk with 18 different filters rotates 15 times every minute. The filters select different UV wavelengths, which are passed to a sensor and recording computer. The sensor is kept dry and at a constant temperature to get a stable response. Smithsonian Institution scientists pioneered atmospheric monitoring in the late 1800s.