Which water meter type utilizes a magnetic field to determine flow?

• A. Ultrasonic
• B. Magnetic
• C. Insertion
• D. Venturi

Answer: (B)

Magnetic flow meters use Faraday’s law: when a conductive fluid moves through a magnetic field, a voltage is generated across electrodes placed in the pipe, perpendicular to both the flow and the field. The meter reads this induced voltage, which is proportional to the fluid’s velocity, and from that it calculates the flow rate through the pipe’s cross-sectional area. Because there are no moving parts, these meters are durable and well-suited for typical waters with ions that carry current.

Ultrasonic meters, by contrast, measure flow with sound waves and do not rely on a magnetic field. Venturi meters determine flow from a pressure difference created by a constriction, not a magnetic field. An insertion meter describes how the sensor is installed (inserted into the pipe) rather than the measurement principle, and it can be used with different technologies.