Water, being a limited and vulnerable natural resource, must be protected and economically administrated. A correct administration requires, among other things, flow measurements in order to control water consumption. Flowmeters whose characteristic equations are based on a pressure drop are generally non-linear, the flow measured not being proportional to the pressure drop. The flowmeters mostly used are those having local hydraulic resistance. Usually the local hydraulic resistance for liquid flows is obtained by decreasing the flowing section as, for example, in the Venturi tube. Although Venturi tubes have a high reliability, their disadvantages consist in the need for accurate manufacture, high price and the difficulty of replacement. These drawbacks may be avoided by realizing a flow transducer with a straight tube and a magnetic liquid manometer. In this context we present, for the first time, the operating principle and the “voltage–flow” characteristic curve of an inductive ferrofluids flow transducer for water. The transducer uses the properties of the magnetic liquid and has no moving parts (components). It can be used in steady flow conditions. The device can be adapted practically to any flow range by using a straight pipe of suitable section and an adequate U-tube manometer.