Electromagnetic Flowmeter

Electromagnetic flowmeter is a new type of flow measuring instrument developed rapidly with the development of electronic technology in the 1960s. It is made according to Faraday's law of electromagnetic induction and is used to measure the volumetric flow of a conductive fluid. Due to its unique advantages, it has been widely used in the measurement of various conductive liquids in industry. For example, measuring various acids, alkalis, salts and other corrosive liquids; various flammable, explosive media; various industrial sewage, pulp, mud and so on.

The main features of the electromagnetic flowmeter are: 1 The transmitter of the electromagnetic flowmeter has a simple structure, no moving parts, and no throttling components that hinder the flow of the fluid, so that when the fluid passes, it does not cause any additional pressure loss. It does not cause problems such as wear and blockage, and is especially suitable for measuring slurry with solid particles, liquid-solid two-phase fluid such as sewage, and various viscous slurries. Similarly, since it has no moving parts in its structure, it can be made of a corrosion-resistant insulating lining and a corrosion-resistant material to provide an excellent corrosion resistance, making it suitable for measurement of various corrosive media. 2 Electromagnetic flowmeter is a kind of volume flow measuring instrument. It is not subject to the temperature of the measured medium during the measurement. The effect of viscosity, density and conductivity (within a certain range). Therefore, the electromagnetic flowmeter can be used to measure the flow of other conductive liquids only after water calibration, without the need for additional corrections. 3 The range of the electromagnetic flowmeter is extremely wide, and the range ratio of the same electromagnetic flowmeter can reach 1:100. In addition, the electromagnetic flowmeter is only proportional to the average flow velocity of the measured medium, and is independent of the flow state (laminar or turbulent flow) under an axisymmetric distribution. 4 Electromagnetic flowmeter has no mechanical inertia and is sensitive. It can measure instantaneous pulsating flow and has good linearity. Therefore, the measurement signal can be linearly converted into a standard signal output directly by the converter, and can be indicated locally or remotely.

Although the electromagnetic flowmeter has the above-mentioned excellent characteristics, it still has some shortcomings, so that it is limited in use. The main points are as follows: 1 Electromagnetic flowmeters cannot be used to measure gases, vapors, and liquids containing large amounts of gas. 2 Electromagnetic flowmeter can not be used to measure liquid medium with low conductivity. The conductivity of liquid medium to be tested should not be lower than 10~5 (S/cm), which is equivalent to the conductivity of distilled water. There is nothing to do with petroleum products or organic solvents. 3 Due to the temperature limitation of the measuring tube insulation lining material, the current industrial electromagnetic flowmeter cannot measure high temperature and high pressure fluid. 4 The electromagnetic flowmeter is affected by the flow velocity distribution. Under the condition of axisymmetric distribution, the flow signal is proportional to the average flow velocity. Therefore, the electromagnetic flowmeter must also have a length of front and rear straight pipe sections. 5 Electromagnetic flowmeters are susceptible to external electromagnetic interference.