How do electromagnetic (mag) flow meters differ from ultrasonic meters?

Mag meters generate a magnetic field and measure the voltage induced as conductive fluid flows through, while ultrasonic meters use sound waves and either transit‑time or Doppler principles. Mag meters are widely used on full, pressurized pipes with conductive liquids (e.g., force mains), whereas ultrasonic meters can be clamp‑on, inline, or open‑channel and are often chosen where non‑intrusive or retrofittable installations are needed.​