A method of determining a fraction of one or more phases in a multi-phase fluid in a conduit is provided. The method includes exciting (602) a sensing device to cause emission of electromagnetic waves of a range of frequencies into a multi-phase fluid. The sensing device comprises an antenna and a dielectric layer, selected to cause resonance in at least one of a first set of frequencies or a second set of frequencies based on a flow state of the multi-phase fluid, when placed proximate to the multi-phase fluid. The method also includes receiving (604) transmitted or reflected electromagnetic waves from the multi-phase fluid. The flow state of the multi-phase fluid is selected (606) based on a classification parameter. Fractions are determined (608) utilizing at least one fraction determination model that is selected based on the flow state of the multi-phase fluid.