Structure and function of electromagnetic flow meter, analysis of cleaning electrical level method
2024-05-29
Electromagnetic flow meters are mainly used to measure the volume flow of conductive liquid and slurry in closed pipelines, including acid, alkali, salt and other highly corrosive liquids. Electromagnetic flowmeters are widely used in petroleum, chemical, metallurgical, textile, food, pharmaceutical, paper and other industries, as well as environmental protection, municipal management, water conservancy construction and other fields.
Electromagnetic flowmeter
The measuring principle of electromagnetic flowmeter is Faraday's law of electromagnetic induction, and the main components of the sensor are: measuring tube, electrode, excitation coil, iron core and yoke housing. An instrument to measure the flow of conductive fluid according to the electromotive force induced by the conductive fluid through the external magnetic field, because of its high measurement accuracy, stable performance and long working time, it can be seen in various industries.
Electromagnetic flowmeter structure composition analysis:
Magnetic circuit system: Its role is to produce a uniform DC or AC magnetic field. The DC magnetic circuit is realized with a magnet, which has the advantage that the structure is relatively simple and the interference from the AC magnetic field is less, but it is easy to polarize the electrolyte liquid in the measurement catheter, so that the positive electrode is surrounded by negative ions, and the negative electrode is surrounded by positive ions, that is, the polarization phenomenon of the electrode, and causes the internal resistance between the two electrodes to increase, which seriously affects the normal operation of the instrument. When the diameter of the pipe is large, the magnet is correspondingly large, bulky and uneconomical, so the electromagnetic flowmeter generally uses an alternating magnetic field, and is generated by a 50HZ power supply excitation.
Flowmeter coil
Measuring catheter: Its function is to let the conductive liquid to be measured through. In order to make the magnetic flux shunt or short circuit when the magnetic force line passes through the measuring catheter, the measuring catheter must be made of non-magnetic, low electrical conductivity, low thermal conductivity and a certain mechanical strength material, which can be selected from non-magnetic stainless steel, glass fiber reinforced plastic, high-strength plastic, aluminum, etc.
Electrode: Its role is to elicit the induced potential signal proportional to the measurement. The electrodes are generally made of non-magnetic stainless steel and are required to be flush with the lining so that fluid can pass through unimpeded. Its installation position should be in the vertical direction of the pipeline to prevent sediment accumulation on it and affect the measurement accuracy.
Shell: made of ferromagnetic material, it is the outer cover of the distribution system excitation coil and isolates the interference of the external magnetic field.
Lining: There is a complete electrical insulating lining on the inside of the measuring catheter and the flange sealing surface. It is in direct contact with the measured liquid, and its role is to increase the corrosion resistance of the measuring conduit and prevent the induced potential from being short-circuited by the metal measuring conduit wall. Lining materials are mostly corrosion resistant, high temperature resistant, wear-resistant polytetrafluoroethylene plastics, ceramics and so on.
Converter: The induced potential signal generated by the liquid flow is very weak, greatly affected by various interference factors, the role of the converter is to amplify the induced potential signal and convert it into a unified standard signal and inhibit the main interference signal. Its task is to convert the induced potential signal Ex detected by the electrode into a unified standard DC signal by amplification.
Then the electromagnetic flowmeter is used in many occasions to measure viscous, or sludge such a medium, it is easy to cover the electromagnetic flowmeter measurement electrode, resulting in inaccurate measurement of the impact, therefore, you need to regularly clean the electromagnetic flowmeter, the following are several ways of cleaning:
Electrochemical method: There are electrochemical phenomena of metal electrode in electrolyte fluid. According to the principle of electrochemistry, there is an interfacial electric field between the electrode and the fluid, and the interface between the electrode and the fluid is caused by the double electric layer existing between the electrode and the fluid.
Converter diagram
It is found that most inorganic anions are surface active substances with typical ion adsorption, while inorganic cations have very little surface activity. Therefore, the electrochemical cleaning electrode only considers the case of anion adsorption.
The adsorption of anions is closely related to the electrode potential, and the adsorption mainly occurs in the potential range that is more correct than the zero charge potential, that is, the electrode surface with different charge. On the surface of the electrode with the same charge, when the residual charge density is slightly larger, the electrostatic repulsion is greater than the adsorption force, and the anion is quickly desorbed, which is the principle of electrochemical cleaning.
Flowmeter converter
Mechanical removal method: Mechanical removal method is to achieve electrode removal by installing a special mechanical structure on the electrode. Generally, mechanical scrapers are used. A scraping device is made of stainless steel with a thin shaft, and a mechanical seal is adopted between the thin shaft and the hollow electrode to prevent the outflow of the medium, so the mechanical scraping device is composed. When the thin shaft is turned from the outside, it is turned against the plane of the electric extremes to scrape off dirt. The scraper can be manually or automatically scraped with a thin shaft driven by a motor.
Ultrasonic cleaning method: The ultrasonic voltage of 45~65kHz generated by the ultrasonic generator is added to the electrode, so that the ultrasonic energy is concentrated on the contact surface between the electrode and the medium, so as to use the ultrasonic ability to crush the dirt to achieve the purpose of cleaning.
Flowmeter cleaning tank
Electric shock piercing method: This method uses AC high voltage regularly added between the electrode and the medium, generally adding 30~100V. As the electrode is attached, its surface contact resistance becomes larger, the applied voltage is almost concentrated on the attachment, and the high voltage will break down the attachment, and then be washed away by the fluid.
Trend chart
Safe and reliable cleaning method, the use of electric shock threading method must be in the flow meter interrupt measurement, the signal line between the sensor and the converter is disconnected, the AC high voltage directly on the sensor signal output terminal for cleaning. It becomes an asymmetric common mode voltage. The asymmetric common-mode voltage becomes a differential mode signal, resulting in zero shift.
Regular electrode cleaning will extend the service life of the electromagnetic flowmeter. It should be known that once the electromagnetic flowmeter fails, the cost of maintenance will be relatively high, and only in the usual use can regular maintenance be done in order to reduce unnecessary losses and expand the value of the product.
Electromagnetic flowmeter is to convert the change of flow rate into the change of induction potential. The larger the measured flow rate, the greater the induced potential, the higher the flow rate, the higher the induced potential, and the lower the induced potential. This induced potential is amplified and converted into a uniform standard signal (such as 4-20mA) output.
If you want to know more about the flow meter or flow meter selection, please consult the Aister flow meter manufacturer email: sales@aistermeter.com for help.
The measuring principle of electromagnetic flowmeter is Faraday's law of electromagnetic induction, and the main components of the sensor are: measuring tube, electrode, excitation coil, iron core and yoke housing. An instrument to measure the flow of conductive fluid according to the electromotive force induced by the conductive fluid through the external magnetic field, because of its high measurement accuracy, stable performance and long working time, it can be seen in various industries.
Electromagnetic flowmeter structure composition analysis:
Magnetic circuit system: Its role is to produce a uniform DC or AC magnetic field. The DC magnetic circuit is realized with a magnet, which has the advantage that the structure is relatively simple and the interference from the AC magnetic field is less, but it is easy to polarize the electrolyte liquid in the measurement catheter, so that the positive electrode is surrounded by negative ions, and the negative electrode is surrounded by positive ions, that is, the polarization phenomenon of the electrode, and causes the internal resistance between the two electrodes to increase, which seriously affects the normal operation of the instrument. When the diameter of the pipe is large, the magnet is correspondingly large, bulky and uneconomical, so the electromagnetic flowmeter generally uses an alternating magnetic field, and is generated by a 50HZ power supply excitation.
Flowmeter coil
Measuring catheter: Its function is to let the conductive liquid to be measured through. In order to make the magnetic flux shunt or short circuit when the magnetic force line passes through the measuring catheter, the measuring catheter must be made of non-magnetic, low electrical conductivity, low thermal conductivity and a certain mechanical strength material, which can be selected from non-magnetic stainless steel, glass fiber reinforced plastic, high-strength plastic, aluminum, etc.
Electrode: Its role is to elicit the induced potential signal proportional to the measurement. The electrodes are generally made of non-magnetic stainless steel and are required to be flush with the lining so that fluid can pass through unimpeded. Its installation position should be in the vertical direction of the pipeline to prevent sediment accumulation on it and affect the measurement accuracy.
Shell: made of ferromagnetic material, it is the outer cover of the distribution system excitation coil and isolates the interference of the external magnetic field.
Lining: There is a complete electrical insulating lining on the inside of the measuring catheter and the flange sealing surface. It is in direct contact with the measured liquid, and its role is to increase the corrosion resistance of the measuring conduit and prevent the induced potential from being short-circuited by the metal measuring conduit wall. Lining materials are mostly corrosion resistant, high temperature resistant, wear-resistant polytetrafluoroethylene plastics, ceramics and so on.
Converter: The induced potential signal generated by the liquid flow is very weak, greatly affected by various interference factors, the role of the converter is to amplify the induced potential signal and convert it into a unified standard signal and inhibit the main interference signal. Its task is to convert the induced potential signal Ex detected by the electrode into a unified standard DC signal by amplification.
Then the electromagnetic flowmeter is used in many occasions to measure viscous, or sludge such a medium, it is easy to cover the electromagnetic flowmeter measurement electrode, resulting in inaccurate measurement of the impact, therefore, you need to regularly clean the electromagnetic flowmeter, the following are several ways of cleaning:
Electrochemical method: There are electrochemical phenomena of metal electrode in electrolyte fluid. According to the principle of electrochemistry, there is an interfacial electric field between the electrode and the fluid, and the interface between the electrode and the fluid is caused by the double electric layer existing between the electrode and the fluid.
Converter diagram
It is found that most inorganic anions are surface active substances with typical ion adsorption, while inorganic cations have very little surface activity. Therefore, the electrochemical cleaning electrode only considers the case of anion adsorption.
The adsorption of anions is closely related to the electrode potential, and the adsorption mainly occurs in the potential range that is more correct than the zero charge potential, that is, the electrode surface with different charge. On the surface of the electrode with the same charge, when the residual charge density is slightly larger, the electrostatic repulsion is greater than the adsorption force, and the anion is quickly desorbed, which is the principle of electrochemical cleaning.
Flowmeter converter
Mechanical removal method: Mechanical removal method is to achieve electrode removal by installing a special mechanical structure on the electrode. Generally, mechanical scrapers are used. A scraping device is made of stainless steel with a thin shaft, and a mechanical seal is adopted between the thin shaft and the hollow electrode to prevent the outflow of the medium, so the mechanical scraping device is composed. When the thin shaft is turned from the outside, it is turned against the plane of the electric extremes to scrape off dirt. The scraper can be manually or automatically scraped with a thin shaft driven by a motor.
Ultrasonic cleaning method: The ultrasonic voltage of 45~65kHz generated by the ultrasonic generator is added to the electrode, so that the ultrasonic energy is concentrated on the contact surface between the electrode and the medium, so as to use the ultrasonic ability to crush the dirt to achieve the purpose of cleaning.
Flowmeter cleaning tank
Electric shock piercing method: This method uses AC high voltage regularly added between the electrode and the medium, generally adding 30~100V. As the electrode is attached, its surface contact resistance becomes larger, the applied voltage is almost concentrated on the attachment, and the high voltage will break down the attachment, and then be washed away by the fluid.
Trend chart
Safe and reliable cleaning method, the use of electric shock threading method must be in the flow meter interrupt measurement, the signal line between the sensor and the converter is disconnected, the AC high voltage directly on the sensor signal output terminal for cleaning. It becomes an asymmetric common mode voltage. The asymmetric common-mode voltage becomes a differential mode signal, resulting in zero shift.
Regular electrode cleaning will extend the service life of the electromagnetic flowmeter. It should be known that once the electromagnetic flowmeter fails, the cost of maintenance will be relatively high, and only in the usual use can regular maintenance be done in order to reduce unnecessary losses and expand the value of the product.
Electromagnetic flowmeter is to convert the change of flow rate into the change of induction potential. The larger the measured flow rate, the greater the induced potential, the higher the flow rate, the higher the induced potential, and the lower the induced potential. This induced potential is amplified and converted into a uniform standard signal (such as 4-20mA) output.
If you want to know more about the flow meter or flow meter selection, please consult the Aister flow meter manufacturer email: sales@aistermeter.com for help.
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