A turbine flow meter is a precision instrument for measuring the flow rate and total volume of liquids passing through a pipe. It uses a rotating turbine wheel or rotor placed inside the flow path — as fluid flows through, it causes the turbine to spin, and the rate of rotation is proportional to the flow velocity. When you see DN15 or DN25, that refers to the nominal pipe diameter: DN15 → 15 mm diameter pipe (≈ ½ inch) DN25 → 25 mm diameter pipe (≈ 1 inch) These are common sizes for smaller pipework used in fuel lines, water lines, or industrial machines.