When the fluid filled in the pipeline flows through the orifice plate, local contraction occurs, the flow bundle is concentrated, the flow velocity increases, and the static pressure decreases. Therefore, a static pressure difference is generated before and after the orifice plate, which has a certain functional relationship with the flow rate. The larger the flow rate, the greater the pressure difference.

The differential pressure signal is transmitted to the differential pressure transmitter through a pressure conduit, converted into a 4-20mA.DC standard signal, and displayed on the flow meter to show the instantaneous and cumulative flow inside the pipeline.