Instruments for measuring fluid flow are collectively referred to as flowmeter or flow meter. Flowmeter is one of the most important instruments in industrial measurement. With the development of industrial production, the accuracy and range of flow measurement is more and more high, and the flow measurement technology is changing rapidly. In order to adapt to a variety of uses, various types of flowmeter came out successively. More than 100 kinds of flowmeter have been put into use now. From different point of view, Flowmeter has different classification method. There are two kinds of classification methods commonly used, one is according to the measurement principle of flowmeter to classify: second, according to the structure principle of flowmeter classification.
I. Classification according to the principle of measurement
(1) Mechanics principle: the instrument which belongs to this kind of principle has the differential pressure type and the rotor type using Bernoulli's theorem, the impulse type of the momentum theorem and the movable tube type; Using the direct mass of Newton's second law, the target of the principle of fluid momentum, the turbine type using the theorem of angular momentum, the vortex type of the principle of fluid oscillation and the vortex-type, the Pitot-type with the total hydrostatic pressure difference and the volume type and weir, trough type and so on.
(2) Electricity principle: the instrument used for this kind of principle has electromagnetism type, differential capacitance type, inductance type, strain resistance type and so on.
(3) Principle of acoustics: ultrasonic flow measurement using acoustic principle. Acoustic type (shock wave type) and so on.
(4) Thermal principle: the use of thermal principle to measure the flow of heat, direct calorimetry, indirect calorimetry and so on.
(5) Optical principle: laser, photoelectric type and so on are belong to this kind of principle instrument.
(6) The original principle of physics: NMR, nuclear radiation and so on is the instrument of this kind of principle.
(7) Other principles: the principle of marking (tracer principle, NMR principle), and related principles.