This category encompasses measurement instruments that determine the concentration of specific components in liquids and gases. Used for quality control and process control in chemical plants, food manufacturing, water treatment, and semiconductor manufacturing. Includes refractometers, conductivity meters, pH meters, dissolved oxygen meters, turbidity meters, salinity meters, sugar content meters, and alcohol concentration meters, classified into inline and sampling types. Covers a wide range from digital display and analog output to communication-enabled models, essential for continuous monitoring and quality inspection in manufacturing processes. Distinguished from flow meters and pressure gauges by measuring component analysis, positioned as specialized equipment for compositional analysis.