Abstract: In an ultrasonic flowmeter of the time difference type using annular ultrasonic transducers, to obtain an accurate flow volume without correction by actual flow, from theoretical formulas which are taking properties of the fluid such as density, and dimension, and properties of the measuring tube into consideration.

Abstract: A mass flow rate measuring apparatus includes a pair of velocity detecting electrodes spaced by a portion of a wider density detection electrode so as to eliminate any mutual interference between the velocity detecting electrodes. A temperature compensation circuit is used to compensate for errors in the density measurement otherwise caused by the temperature characteristic of the flow pipe and the carrier medium.

Abstract: An electromagnetic fluid flowmeter wherein two arc-shaped, circular segment electrode plates B.sub.1, B.sub.2 are disposed horizontally opposite each other on the internal periphery of a tubular conduit M, and are separated by vertically opposed, convex insulators D.sub.1, D.sub.2. The respective dimensional relationships of the electrode plates and insulators, and the flux pattern of the magnetic field within the conduit, are geometrically determined and configured such that the induced current flow between the electrode plates is always proportional to the fluid flow rate, even when a free fluid surface exists within the conduit and regardless of the level of the free surface.

Abstract: An electromagnetic fluid flowmeter including two arc-shaped, circular segment electrical insulating bodies B.sub.1, B.sub.2 disposed vertically opposite each other on the internal periphery of a tubular conduit M, and a pair of horizontally opposed, convex electrodes D.sub.1, D.sub.2. The respective dimensional relationships of the electrodes and insulating bodies, and the flux pattern of the magnetic field within the conduit, are geometrically determined and configured such that voltage induced between the electrodes is always proportional to the fluid flow rate regardless of the flow velocity distribution within the conduit.