Abstract: A coriolis-type mass flow transducer comprises a straight tube 10 through which a fluid whose mass flow rate is to be measured is arranged to flow while the tube is set into transverse resonant vibration in its second overtone mode. Mass flow is determined by measuring the phase difference between the vibration at two points along the tube 10. Such a transducer exhibits an offset at zero flow, which can vary with time. These variations are minimized by minimizing the damping effects on the tube 10 of bellows 6, 7 used to connect tube 10 in a flow line, and then corrected by measuring the amplitude ratio of the vibrations at the two points, and correcting the initially-determined offset in dependence upon changes in this amplitude ratio.