It operated on the principle that, when flowing fluid flow through obstruction plced in direction of flow, it create pressure drop called P.This P is proportion to square root of flow flowing liquidsteamgas inside the pipe. Orifice plate base flow meter consist of :- Integral orifice plateDifferntial Pressure TransmitterPressure TransmitterTemp. SensorMeasurement precision 0.3, Tenfold of Orifice PlateRequirement of straight pipe less than 0.5D