Specialized equipment category for precision measurement of specific gravity (density) of liquid and solid materials. Includes digital specific gravity meters, floating hydrometers, vibrating density meters, etc., used for quality control of metalworking fluids, chemicals, resin materials, fuel oils, and other substances. Implements density-based quality assessment in material receiving inspection, process control, and product shipping inspection during manufacturing processes. Classified by measurement principles such as Archimedes principle and vibrating tube method, with temperature compensation function models available. Unlike hardness testers and tensile testing machines, these are physical property measurement devices specialized for evaluating material density characteristics.