Abstract: The invention relates to a process for monitoring the functioning of a liquid-liquid extraction column in which non-mixing liquids L1 and L2 circulate in counter-current.To this end, an ultrasonic signal is emitted at point Pn of the decanter and this ultrasonic signal is detected at Point P'n located at distance H from point Pn and the time t.sub.n taken by this signal to cover distance H is determined; the speed v.sub.2 of propagation of an ultrasonic signal in the liquid medium near point Pn, preferably constituted by pure liquid L2, is also determined, as well as the speed v.sub.1 of propagation of the same ultrasonic signal in the liquid medium near the point P'n, i.e.

Abstract: An ultrasonic flowmeter for measuring the rate of flow of a fluid, comprising a conduit and two acoustic probes placed on a line inclined with respect to the axis of said conduit. The active end of the probes are bathing in an annular chamber formed by a sleeve extending the inner wall of the conduit in the measuring zone and a swell in the inner wall of the conduit, and in which the fluid may penetrate.

Abstract: Device for measuring the flow speed of a fluid, comprising sound wave transmitting-receiving probes placed in the fluid flow, wave generating means, transforming means for exploiting the electrical signals, such as amplifiers, counting circuits and integrating circuits, characterized in that a plurality of integrators with variable time constant are periodically put to zero once their outputs have been sampled, said operations being made by analog switches.