Orifice Meter or orifice Plate: It is a device used for measuring the rate of flow of a fluid through a pipe. It is Cheaper device as compared to venturimeter. It also works on the same principle as that of venturimeter. It consist of flat circular plate which has a cirxular sharp edged hole called orifice, which is concentric with the pipe. The orifice diameter is kept generally 0.5 times the diameter of the pipe, though it may vry from 0.4 to 0.8 times the pipe diameter. A differential manometer is connected at section (1) , which is at a distance of about 1.5 to 2.0 times the pipe diameter upstream from the orifice plate, and at section (2), which is at a distance of about half the diameter of the orifice on the downstream side from the orifice plate.