Orifice plate

An orifice plate is a device which measures rate of fluid flow. It uses the same principle as the Venturi nozzles, namely Bernoulli's principle. It basically says that there is a relationship between the pressure of the fluid and the velocity of the fluid – velocity increases, the pressure decreases and vice versa.

An orifice plate is basically a thin plate with a hole in the middle. It is usually placed in a pipe in which fluid flows.

As fluid flows through the pipe it has a certain velocity (which we want to measure) and a certain pressure (which is quite easily measured). When the fluid reaches the orifice plate, with the hole in the middle, the fluid is forced to converge to go through the small hole. As it does so, the velocity and the pressure changes. By measuring the difference in fluid pressure between the normal pipe section and just after the orifice plate, we can find the velocity of the fluid flow by applying Bernoulli's equation.