(1) Mechanical principles: Instruments belonging to this type of principle include differential pressure type and rotor type using Bernoulli's theorem; impulse type and movable tube type using momentum theorem; direct mass type using Newton's second law; target type using the principle of fluid momentum; turbine type using the angular momentum theorem; Vortex type and Vortex type using the principle of fluid oscillation; pitot tube type and volumetric type and weir, trough type using the total static pressure difference, etc.

(2) Electrical principle: Instruments used for this type of principle include electromagnetic type, differential capacitance type, inductance type, strain resistance type, etc.

(3) Acoustic principle: Flow measurement using acoustic principles includes ultrasonic type, acoustic type (shock wave type), etc.

(4) Thermal principle: There are thermal type, direct calorimetric type, indirect calorimetric type, etc. that use thermal principles to measure flow.

(5) Optical principle: Laser type, photoelectric type, etc. are instruments belonging to this type of principle.

(6) Originated from physical principles: Nuclear magnetic resonance type, nuclear radiation type, etc. are instruments that belong to this type of principle.

(7) Other principles: There are labeling principles (tracing principles, nuclear magnetic resonance principles), related principles, etc.