1. Faraday's Law of Induction: The electromagnetic flow meter works based on Faraday's Law, which states that a voltage is induced in a conductor moving through a magnetic field. In this case, the conductive liquid itself is the moving conductor.
2. Independence from Physical Properties: The induced voltage ($E$) is given by the equation:
$$E = B \cdot v \cdot D$$
Where:
• $B$ is the magnetic field strength.
• $v$ is the average velocity of the liquid.
• $D$ is the diameter of the pipe.
3. Analysis: Note that
density ($\rho$) does not appear in the voltage equation. As long as the liquid has a minimum level of electrical conductivity, the meter provides an accurate flow rate measurement regardless of changes in density, viscosity, temperature, or pressure.
In contrast, rotameters (buoyancy-based) and Venturi/Orifice meters (pressure-based) are all significantly affected by the density of the fluid.