Abstract: A meter to measure the mass flow rate of gases passing through a flow tube, with the flow tube being incorporated as part of a flow tube assembly mounted for continuous rotation about a spin axis and simultaneous deflection about a measurement axis. Also incorporated as part of the flow tube assembly are counterbalance masses mounted so as to provide radial forces that oppose Coriolis/gyroscopic forces generated from the flow tube. The flow tube assembly is mounted for deflection about the measurement axis using low friction rotary seals. The deflections of the flow tube assembly about the measurement axis have a linear relation to the mass flow rate of gas passing through the flow tube.