Classification based on measurement principles

1. Mechanics principle: Instruments belonging to this type of principle include differential pressure type and rotor type using Bernoulli's theorem; Using the momentum theorem's impulse formula and movable tube formula; Using the direct mass formula of Newton's second law; Targeting based on the principle of fluid momentum; Turbine type using the angular momentum theorem; Vortex type and vortex street type utilizing the principle of fluid oscillation; Pitot tube type, volumetric type, weir, groove type, etc. utilizing the total static pressure difference.
2. Electrical principles: Instruments used for such principles include electromagnetic, differential capacitive, inductive, strain resistance, etc.
3. Acoustic principle: There are ultrasonic and acoustic (shock wave) methods that use acoustic principles for flow measurement.
4. Thermal principle: There are various methods for measuring flow rate using thermal principles, such as calorimetry, direct calorimetry, indirect calorimetry, etc.
5. Optical principle: Laser type, photoelectric type, etc. are instruments belonging to this type of principle.
6. Atomic physics principles: Nuclear magnetic resonance, nuclear radiation, and other instruments belong to such principles
7. Other principles: including labeling principles (tracing principles, nuclear magnetic resonance principles), related principles, etc.