The SQ-515 is an amplified full-spectrum quantum sensor with a 0 to 5 V output. The sensor incorporates a blue-enhanced silicon photodiode and custom optical filters with a rugged, self-cleaning sensor housing design, anodized aluminum body with acrylic diffuser, and high-quality cable terminating in pre-tinned pigtail leads for easy connection to dataloggers and controllers. Typical applications include PPFD measurement over plant canopies in outdoor environments, greenhouses, and growth chambers, and reflected or under-canopy (transmitted) PPFD measurements in the same environments. Quantum sensors are also used to measure PAR/PPFD in aquatic environments, including salt water aquariums where corals are grown. Sensor includes IP68 marine-grade stainless-steel cable connector to simplify sensor removal and replacement for maintenance and recalibration.