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hydrometer hy·drom·e·ter (hī-drŏm'ĭ-tər)
An instrument used to determine specific gravity, especially a sealed graduated tube, weighted at one end, that sinks in a fluid to a depth indicating the fluid's specific gravity. Also called gravimeter.
An instrument used to measure the density of a liquid as compared to that of water. Hydrometers consist of a calibrated glass tube ending in a weighted glass sphere that makes the tube stand upright when placed in a liquid. The lower the density of the liquid, the deeper the tube sinks.
device for measuring some characteristics of a liquid, such as its density (weight per unit volume) or specific gravity (weight per unit volume compared with water). The device consists essentially of a weighted, sealed, long-necked glass bulb that is immersed in the liquid being measured; the depth of flotation gives an indication of liquid density, and the neck can be calibrated to read density, specific gravity, or some other related characteristic