Abstract: A device for ascertaining flow rate through one or more valves and/or pumps simultaneously. A transducer (T.10) is connected to the valve actuator member and displaceable or rotatable therewith and produces an output determined by the valve position. The output of the transducer is supplied to an electronic processing mean (13) programmed to calculate the flow rate from data relating to the flow characteristics of the or each valve and data relating to the flow characteristics of the fluid concerned and the temperature and pressure and to display the calculated flow rate or utilize the calculated flow rate to control the valve position to regulate the flow rate.