Devices and methods for measuring the fraction of a liquid in a wet gas flow are described, the device including one or more light sources emitting at a first wavelength at which the liquid is highly absorbing and emitting at a second wavelength close to the first wavelength and at which the liquid is not highly absorbing; and one or more sensor for detecting the transmittance of the light at the first and second wavelengths through said gas flow, the device further including processing means for determining a liquid fraction of the liquid in the wet gas flow by correcting the transmittance measured at the first wavelength for the effects of scattering using the transmittance measured at the second wavelength. By making use of cross-correlations or know flow rate meters the device can be used as a flow meter.