I. Classification according to measurement principles

(1) Mechanical principle: Instruments belonging to this principle include differential pressure type and rotor type using Bernoulli's theorem;Using the momentum theorem of impulse formula, movable tube type;Using the direct mass formula of Newton's second law;Target type using fluid momentum principle;Turbine formula using angular momentum theorem;Vortex type and vortex street type using the principle of fluid oscillation;Pitot tube type, displacement type, weir type, trough type and so on.

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

(3) Acoustic principle: Ultrasonic and acoustic (shock wave) are used for flow measurement.

(4) Thermal principle: Thermal principle is used to measure the flow with heat, direct calorimetry, indirect calorimetry, etc.

(5) Optical principle: Laser and photoelectric instruments belong to such principle.

(6) Due to the physical principle: NUCLEAR magnetic resonance type, nuclear radiation type, etc. are instruments belonging to this principle.

(7) Other principles: labeling principle (tracer principle, NUCLEAR magnetic resonance principle), related principle, etc.

Two, according to the flowmeter structure principle classification

According to the actual situation of current flowmeter products and the structure principle of the flowmeter, it can be roughly classified into the following types:

1. Positive displacement flowmeter

The volumetric flowmeter is equivalent to a vessel of standard volume, which continuously measures the flowing medium.The larger the flow, the more the number of measurements, the higher the output frequency.The volumetric flowmeter is simple in principle and suitable for measuring high viscosity and low Reynolds number fluids.According to the different shape of the rotary body, the current products are divided into: suitable for measuring the flow of liquid elliptical gear flow meter, rotary piston and scraper type flow meter;Servo volumetric flowmeter, membrane flowmeter and rotary flowmeter are suitable for measuring gas flow.