Abstract: A flowmeter is provided for receiving a plurality of fluid streams and providing signals representative of the mass flow rate of each stream and the differential mass flow rate of any selected pair of the streams. A housing defines a flow channel to accommodate each stream to be measured. An impeller is rotatably mounted in each channel to impart measured angular momentum to the fluid flowing in that channel and all of the impellers are driven by a common turbine and shaft. The impellers are each resiliently coupled to the shaft so that the impellers lag behind the shaft by an amount proportional to the angular momentum imparted by each impeller to the fluid in its respective channel.