Abstract: Apparatus for continuously measuring rates of flow of a liquid has two containers arranged serially in the liquid flow path and each associated with a self-levelling balance beam. Beam displacement is measured capacitively and used to alter current fed to a coil tending to maintain the beam level. The magnitudes of the currents necessary to maintain the beams level is a measure of the liquid level in the containers and is used to keep the liquid levels between pre-determined upper and lower values by controlling valves through which the liquid flows into the containers. The differentials of the currents with respect to time when the liquid levels are falling in both containers, are added. If the liquid level in the first container is rising, however, no differential is provided whereas the differential of the second container liquid level, when rising, is supplied to the adder but negatively. The adder provides an output which is a measure of the volume of liquid supplied by the apparatus.