Secchi disk

American  

noun

1. an opaque, white or black-and-white disk used to measure the cloudiness or turbidity of ocean water by the point at which it is no longer visible from the surface.

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Secchi disk Scientific  

1. An instrument used for measuring the clarity of water, especially seawater. It consists of a circular plate divided into alternating black and white quadrants and attached to a long measuring tape. The plate is lowered into the water, and the depth at which it is no longer visible from the surface is recorded. The Secchi disk is named after its inventor, Italian astronomer Angelo Secchi (1818–1878).

2. See also Secchi depth

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Etymology

Origin of Secchi disk

First recorded in 1910–15; named after Pietro Angelo Secchi (1818–78), Italian astronomer who invented it in 1865

Example Sentences

The researchers measure the clarity of the lake by lowering a 10-inch-wide white disk, known as a Secchi disk, into the water and marking at what depth the disk remains visible.

From Los Angeles Times • Aug. 1, 2022