This instrument is specially used to measure the concentration (activity) of K⁺ ions in various water and solutions. When the substance under test is solid, solid-like, dense and biological, plant, it can be measured by decomposition and dissolution. Measuring units can choose pK and g/l, mg/l, μg/l, and ng/l [g (mg, μg, ng, pg)/L]. The instrument will automatically switch display units (g/L, mg/L, μg/L, ng/L) according to the content of K⁺ ions in the substance to be measured. It is easy to use. It is suitable for high precision measurement and test in various disciplines.