What is a Hydrometer?

The specific gravity is the ratio when the mass of a specific substance is compared with the standard substance of the same volume, and water at 4 ° C is generally used as the standard substance. A hydrometer is a device for measuring this density. The term specific density is used for solids, liquids, and gases, but this article describes a device for measuring the specific gravity of liquids. First of all, to summarize the buoyancy acting on an object, when the specific gravity of water is 1, if the specific gravity of the target substance is larger than 1, it will sink in water, and if it is smaller, it will float. The most common floating scale type hydrometer uses this principle. This is a scale that floats on a liquid, reads its scale, and measures its specific density from that value, and has the shape shown in Fig. 1. Schematic diagram of the hydrometer The mainstream hydrometers are the floating type as shown in Fig. 1, but recently there are also load cell type, vibration type, differential pressure type, radiation type, etc., and the display is digital and easier to measure than the conventional one. Products that can be used are also being developed.

Application of Hydrometer

Hydrometers are used in a wide range of fields such as pharmaceuticals, food processing, industry, and scientific research. Specifically, it is as follows. Salinity measurement of seawater Measurement of sugar content of fruits that are the ingredients of juice Concentration measurement of various chemicals used in industry such as semiconductors, plating, battery electrolytes, etc. Measurement of fat content in milk Alcohol content measurement by volume ratio of water in alcohol products Measurement of impurity content in petroleum products

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