Abstract: The disclosure is directed to a device for monitoring the thermodynamic state of a fluid flowing through a conduit. The device generally comprises a first electromechanical transducer acoustically coupled to the conduit, electronic drive means connected to the first electromechanical transducer to provide a driving electrical signal to the first electromechanical transducer whereby the first electromechanical transducer is oscillated to generate mechanical wave energy for transmission through the fluid flow, and a second electromechanical transducer acoustically coupled to the conduit and arranged in a spaced, acoustically coupled relation to the first electromechanical transducer to receive the mechanical wave energy transmitted through the fluid flow and conduit by the first electromechanical transducer and to convert the received mechanical wave energy into an electrical signal.