How Differential Pressure Flow Measurement Works: Bernoulli's Principle in Action! Have you ever wondered how a tiny pressure difference inside a pipe can indicate the entire flow rate? The answer lies in a fundamental law of physics - Bernoulli's Principle. The Core Concept When a fluid passes through a restriction, such as an orifice plate, venturi, or flow nozzle: - The velocity increases at the narrowest point (vena contracta). - Pressure energy is converted into kinetic energy. - Static pre