Abstract: A mass flow meter particularly adapted for measuring the mass flow rate of finely divided coal being transmitted through a conduit, for example, as used in large scale fossil fuel power plants. The invention is particularly related to several embodiments of transducer assemblies mounted to the conduit which enable ultrasound pulses to be transmitted across the conduit and detected such that the downstream drift and attentuation of the pulses can be evaluated and correlated to coal concentration and velocity. In a first embodiment, a pair of transducers on variable pitch mounts are located at diametrically opposite positions across the conduit. The transmitting transducer is aimed upstream with respect to the flow and simultaneously the receiving transducer is aimed downstream a corresponding angular amount such that it receives the transmitted pulse in a manner which produces a maximum amplitude output signal.