Coxeter bobbin flow meter
Date of manufacture:
These flowmeters have parallel walled tubes. The increasing leak required to cause the bobbins to rise to a level proportional to the flow is achieved by drilling a series of small holes in the tubes. The whole assembly of metering tubes is sealed in an outer tube that delivers the gases to the top manifold. Each bobbin rises in increments until the number of holes below it provides a sufficient compound leak that the bobbin can rise no more. The system is not as precise as the rotameter tube, which has a tapered lumen and no side holes.
These flowmeters succeeded the Gwathmay Water Sight Flowmeters originally fitted to the Boyle Machine when that machine was manufactured by Coxeter.