Abstract: A fluid regulating system has an electro-fluidic control loop in which a fluid control pressure indicative of the relationship between an existing fluid condition and a demand signal acts in opposition to a bias pressure on a control member forming part of a transducer, to provide an electrical output representative of the instantaneous position of the control member. The electrical output is arranged to control a regulating device and so regulate the existing fluid condition in the sense to maintain the fluid control pressure substantially constant. The fluid regulating system has advantageous application to metering of L.P.G. to the carburation system of an internal combustion engine.