TOrifice plate is a device used for measuring flow rate. Either volumetric or mass flow rate may be determined, depending on the calculation associated with it. It uses the same principle, namely Bernoulli’s principle which states that there is a relationship between the pressure of the fluid and the velocity of the fluid. When the velocity increases, the pressure decreases and vice versa. Generally orifice plate is a thin plate with hole in the middle or vice versa.