In the physical world, mechanical engineers are frequently required to monitor or control the flow of various fluids through pipes, ducts and assorted vessels. This fluid can range from thick oils to light gasses. While some techniques work better with some groups of fluids, and less well with others, some are not at all suitable for some applications. In this primer on fluid flow instrumentation we will look at a wide variety of flow transducers and their application in the physical world. Flow meter is an instrument used to measure linear, nonlinear, mass or volumetric flow rate of a liquid or a gas. Fluid flow measurement can encompass a wide variety of fluids and applications. Flow meters have proven an excellent devices for measuring flow in the in many different applications such as irrigation fields as it is required for measuring the water needed in irrigation fields in order to avoid damage of crops with excess water and even to save the water as it is most precious resource. Flow meter also serves the purpose of judging the irrigation pipelines as for example lower than normal flow rates may indicate the need for pump repair or leakage of pipelines.