Numerous industrial processes require an exact monitoring of the values for the flow of liquids and gases. The selection of the optimal flow measurement technology depends on the specific application and the type of process media. Crucial criteria here include process pressure and temperature ranges of the medium, viscosity and chemical aggressivity. WIKA offers an extensive portfolio of primary flow elements: among them, orifice plates, meter runs, flow nozzles / Venturi nozzles, Venturi tubes, pitot tubes and restriction orifices. The method most widely used in industrial measurement technology is based on the principle of differential pressure measurement. A narrowing of the cross-section in the pipeline causes a decrease in pressure and a proportional increase in the flow rate. Thus, the exact determination of the differential pressure before and after the restriction is sufficient to calculate the mass flow or the volume flow . The derivation of the quantities is based on the determination of the flow coefficients with the help of the Bernoulli equation. These methods are known as differential pressure methods.