E+H electromagnetic flow meter working principle and operation method

Electromagnetic Flowmeters (EMF for short) are new flow measurement instruments that developed rapidly with the development of electronic technology in the 1950s and 1960s. E+H electromagnetic flowmeter is made according to Faraday's law of electromagnetic induction. Electromagnetic flowmeter is used to measure the volume flow of conductive liquid. Due to its unique advantages, E+H electromagnetic flowmeter has been widely used in the flow measurement of various conductive liquids in industrial processes, such as various acids, alkalis, salts and other corrosive media; E+H electromagnetic flowmeter has various This type of slurry flow measurement has formed a unique application field. Structurally, the E+H electromagnetic flowmeter consists of an electromagnetic flow sensor and a converter. The sensor is installed on the industrial process pipeline. Its function is to linearly convert the liquid volume flow value flowing into the pipeline into an induced potential signal, and send this signal to the converter through a transmission line. The converter is installed not too far away from the sensor. It amplifies the flow signal sent by the sensor and converts it into a standard electrical signal proportional to the flow signal for output for display, accumulation and adjustment control.

The working principle and operation method of the E+H electromagnetic flowmeter (1) The measurement principle of the E+H electromagnetic flowmeter. According to Faraday’s law of electromagnetic induction, when a conductor moves in a magnetic field and cuts magnetic lines of force, the two sides of the conductor The induced electric potential e is generated at the end, and its direction is determined by the right-hand rule. Its magnitude is proportional to the magnetic induction intensity B of the magnetic field, the length L of the conductor in the magnetic field, and the movement speed u of the conductor. If B, L, and u mutually Vertical, then e=Blu (3-35) is similar to this. In a uniform magnetic field with a magnetic induction intensity B, a non-magnetic pipe with an inner diameter D is placed perpendicular to the direction of the magnetic field. When the conductive liquid flows in the pipe at a flow rate u, the conductive liquid cuts the magnetic lines of force. If a pair of electrodes are installed on both ends of the diameter of the pipe section perpendicular to the magnetic field, it can be proved that as long as the flow velocity distribution in the pipe is axially symmetric, an induced electromotive force will also be generated between the two electrodes: e = BD (3-36) Equation , is the average flow velocity on the pipe section. From this, the volume flow rate of the pipeline can be obtained as: qv=πDUˉ=(3-37) It can be seen from the above formula that the volume flow rate qv has a linear relationship with the induced electromotive force e and the inner diameter D of the measuring tube, and is inversely proportional to the magnetic induction intensity B of the magnetic field. , independent of other physical parameters. This is the measurement principle of E+H electromagnetic flowmeter.

It should be noted that for equation (3-37) to be strictly established, the measurement conditions must meet the following assumptions: ① The magnetic field is a uniformly distributed constant magnetic field; ② The flow rate of the measured fluid is axially symmetrically distributed; ③ The measured liquid is non-magnetic. ;④The conductivity of the measured liquid is uniform and isotropic. E+H electromagnetic flowmeter is composed of a sensor that is in direct contact with the pipeline medium and an upper signal converter. The E+H electromagnetic flowmeter is specially designed with a Chinese LCD display with backlight and wide temperature. It is fully functional and practical, with intuitive display and easy operation. It can reduce other electromagneticThe inconvenience caused by the English menu of the flow meter. In addition, we designed a 4-6 multi-electrode structure to further ensure the measurement accuracy and eliminate the need for a grounding ring at any time, reducing the instrument size and the trouble of installation and maintenance. The E+H electromagnetic flowmeter not only meets the needs of on-site display, but also can output 4~20mA current signals for recording, adjustment and control. It is now widely used in chemical industry, environmental protection, metallurgy, medicine, papermaking, water supply and drainage and other industrial technologies. and management. E+H electromagnetic flowmeter is a flow meter with high precision, high reliability and long service life. Therefore, we are very meticulous in every aspect of the design of product structure, material selection, process formulation, production assembly and factory testing, and also do our own Designed a set of Chinese electromagnetic flowmeter production equipment and flow calibration device to ensure the long-term high quality of the product in terms of software and hardware. (2) Operation method of E+H electromagnetic flowmeter ① Select the corresponding water pump according to the diameter and flow rate of the pipeline for calibration test; ② If the system uses compressed air power, turn on the air compressor to achieve the air source pressure required by the system. To ensure the rapid switching of the commutator and the normal operation of the meter clamp; ③ After the flow meter is correctly installed and connected, it should be powered on and preheated for about 30 minutes in accordance with the requirements of the calibration regulations; ④ If a high-level tank water source is used, the voltage of the pressure-stabilizing water tower should be checked Whether the overflow signal appears. Before the formal test, the calibration medium should be circulated in the pipeline system for a certain period of time in accordance with the requirements of the calibration regulations, and at the same time, check whether there are leaks in the sealing parts of the pipeline; ⑤ Before starting the formal calibration, the calibration medium should be filled with Check the flowmeter sensor, then close the downstream valve for zero adjustment; ⑥ When starting the calibration, open the valve at the front end of the pipeline first, and slowly open the valve behind the flowmeter being tested to adjust the flow rate at the calibration point. ⑦During the calibration process, the flow stability of each flow point should be within 1% to 2% - flow rate method, while the total flow rate method can be within 5%. The temperature change of the calibration medium should not exceed 1°C when completing the calibration process of one flow point, and should not exceed 5°C when completing the entire calibration process. The pressure downstream of the flow meter under test should be high enough to ensure that flash evaporation and cavitation do not occur in the flow pipeline (especially in the short diameter); ⑧ After each test, the front end of the test pipeline should first be The valve is closed, and then the pump is stopped to avoid venting the pressure stabilizing facility. At the same time, all remaining calibration media in the test pipeline must be emptied, and then the control system and air compressor must be shut down.