的工作原理是基于法拉第电磁感应定律。 The working principle of electromagnetic flowmeter is based on Faraday's law of electromagnetic induction. In the electromagnetic flowmeter, the conductive medium in the measuring tube is equivalent to the conductive metal rod in the Faraday test, and the two electromagnetic coils at the upper and lower ends generate a constant magnetic field. When a conductive medium flows, an induced voltage is generated. The two electrodes inside the pipe measure the induced voltage produced. The measuring pipe is electromagnetically isolated from the fluid and the measuring electrode by a non-conductive inner lining (rubber, Teflon, etc.).
的优势 Advantages of electromagnetic flowmeter for sewage measurement
1) The electromagnetic flowmeter is a volume flow measuring instrument. During the measurement process, it is not affected by the temperature, viscosity, and density of the measured medium and its conductivity (within a certain range). Therefore, the electromagnetic flowmeter can be used to measure the flow of other conductive liquids only after it has been calibrated with water. 2) The output of the electromagnetic flowmeter is only proportional to the average flow velocity of the measured medium, and has nothing to do with the flow state (laminar or turbulent) in a symmetrical distribution. Therefore, the range of the electromagnetic flowmeter is extremely wide, and its measurement range can reach 100: 1, and some even reach the operational flow range of 1000: 1. 3) The structure of the sensor of the electromagnetic flowmeter is simple, there are no moving parts in the measuring tube, and there are no throttling parts that hinder fluid flow. Therefore, it will not cause any additional pressure loss when the fluid passes through the flow meter, and it is one of the flow meters with the lowest energy consumption in the flow meter. 4) It can measure the flow of dirty media, corrosive media and suspended liquid-solid two-phase flow. This is because there are no obstructing flow parts inside the measuring tube of the instrument, and only the lining and electrodes of the measuring tube are in contact with the measured fluid, and the material can be selected according to the properties of the measured fluid. For example, using polytrifluoroethylene or polytetrafluoroethylene as the inner lining can measure various corrosive media such as acids, alkalis, and salts; the use of wear-resistant rubber as the inner lining is particularly suitable for measuring the wear of solid particles. Large liquid-solid two-phase flows such as mineral slurry and cement slurry, and various suspended liquids such as fiber-containing liquids and pulp. 5) The caliber range of industrial electromagnetic flowmeters is extremely wide, from a few millimeters to several meters, and there are already actual flow calibration equipment with a caliber of 3m in China, which has laid the foundation for the application and development of electromagnetic flowmeters. 6) The electromagnetic flowmeter has no mechanical inertia and is sensitive in response. It can measure instantaneous pulsating flow, and it can also measure flow in both directions.
电极材料的正确选择 Correct selection of electrode material for electromagnetic flowmeter
The material of the electrode should be selected according to the corrosivity of the liquid being tested, and tests should be performed on special fluids.
Sea water, various chlorides and hypochlorite hydrochloric acid, oxidizing acids (including fuming nitric acid), organic acids, alkalis.
Except for hydrofluoric acid, fuming sulfuric acid, and alkali, other chemical media include boiling point hydrochloric acid, nitric acid, and <175 ° C sulfuric acid.
3.Molybdenum-containing stainless steel (0Cr18Ni12Mo2Ti)
Nitric acid, sulfuric acid <5% at room temperature, boiling phosphoric acid, formic acid, alkaline solution, sulfurous acid, sea water, acetic acid under a certain pressure.
4. Hastelloy C
Hastelloy B (HC, HB)
Sea water, salt water.
5. Platinum (Pt)
Various acids, bases and salts.