Which option is not recommended for Doppler ultrasonic meters?

• A. Ultrasonic Transit-Time
• B. Doppler Ultrasonic
• C. Turbine
• D. Magnetic Flowmeter

Answer: (D)

Doppler ultrasonic meters rely on ultrasound traveling through a flowing fluid and detecting a frequency shift that occurs when the sound waves reflect off moving particles or bubbles. This Doppler shift gives the flow velocity, which is then used to calculate flow rate. Among the options, both ultrasonic transit-time and Doppler ultrasonic are ultrasonic measurement approaches and fit the same family. A turbine meter is a mechanical device with a rotor driven by the flow, not based on ultrasound. A magnetic flowmeter uses Faraday’s law and detects voltage from a conductive fluid moving through a magnetic field; it does not use ultrasonic signals at all. Since the question asks which option isn’t suitable for Doppler ultrasonic meters, the magnetic flowmeter is the one that does not involve ultrasound and thus isn’t compatible with Doppler ultrasonic measurement.