This type of flow meter relates a change in flow rate to the differential pressure across a spring-loaded cone. The cone repositions itself to balance the force.   This, in turn, changes the aperture for the flow. Flow rate has a relationship with the differential pressure of the flow meter and the position of the spring-loaded cone. A differential pressure transmitter is used to indicate flow. This type of differential pressure flow meter technology can be constructed to measure either gas or liquids.