A float is introduced into the tapered tube. This float is lifted up by the liquid which flows through the metering tube. The metering tube being tapered allows the liquid to go past the float at a point where the upward force of the liquid balances the weight of the float. This position of the float is followed by a follower magnet outside the metering tube, the coupling between the two being by virtue of magnets incorporated in either of them The outer follower magnet by mechanical leverage etc transmits this to be read across a scale. This scale is calibrated either in terms of flow rate or percentage. Opening or closing the control valve varies the flow rate in the pipeline, which can be seen as a corresponding reading on the metal tube manometer scale. To open or close the valve click on the gradations on the stepped triangle placed near the control valve.