Electromagnetic flow meters are commonly used flow meters in industrial measurement.Because of its wide application, customers often have problems in their use. Here we will talk about the solution to solve the problem of electromagnetic flow meters for measuring the liquid with large bubbles.Some customers mentioned why the electromagnetic flow meter is equipped with a lining, and we will answer this question from the principle of the electromagnetic flow meter.
In the process of measuring the liquid, there will be many bubbles in the electromagnetic flow meter, which will often lead to errors in the measurement of the flow meter, affecting the use.Generally, the fluid measured by the electromagnetic flow meter will contain some bubbles, and if these bubbles are evenly distributed, it will not affect the measurement, but once the bubble becomes larger,the whole electrode can be covered when passing the electrode, so that the input loop of flow signal is opened instantaneously, causing the output signal to shake.
How to determine the measurement error of electromagnetic flow meter is caused by bubbles contained in the measured liquid?How to deal with this situation? Let's briefly introduce it.
When the measurement result is shaken, the excitation loop current of the magnetic field is cut off immediately. If the meter still displays and is unstable at this time, it is mostly caused by the influence of the bubble.
After determining a large number of bubbles affecting the measurement results of the electromagnetic flow meter, it is necessary to find a relevant solution. If it is judged that a large amount of air bubbles are mixed into the liquid caused by the installation position, such as the electromagnetic flow meter is installed at the high point of the pipeline and the gas is stored or the external air is inhaled to cause the flow meter to shake, replacing the installation position is the most effective solution,but many applications are large diameter or the installation position is not easy to change. It is recommended to install a gas collecting bag and an exhaust valve upstream of the electromagnetic flow meter to eliminate excess gas, reduce the influence factors on the measurement results, and ensure accurate measurement.
Why should the electromagnetic flow meter need lining,this should start from the principle of electromagnetic flow meter.Electromagnetic flow meters generally have a set of coils and two electrodes.The function of the coil is to add an electric field to the fluid. The flowing conductive liquid is equivalent to a conductor. According to Faraday's law of electromagnetic induction, when the conductor cuts the magnetic field line, it will produce an electromotive force proportional to the speed. The role of the electrode is to measure this induced electromotive force, so only the electrode in the measuring tube is connected to the conductive liquid, and the other part is the inner lining,to ensure insulation, electromagnetic flow meter can work normally. If the metal pipe with a magnetic field is also in contact with the liquid, a short circuit between the conductive liquid measured by the electromagnetic flow meter and the metal tube , there will be conduction,and the electric potential will be led away so that the electromagnetic flow meter cannot measure the electric potential.So the inside of the electromagnetic flow meter is lined.
When measuring the flow rate, the conductive liquid flows at a velocity V through a magnetic field perpendicular to the flow direction. The flow of the conductive liquid induces a voltage proportional to the average flow velocity.Its induced voltage signal is detected by two or more electrodes that are in direct contact with the liquid and sent to the converter through the cable for intelligent processing, and then the LCD displays or converts the 4-20ma standard signal and 0-1khz output.In this way, the electromagnetic flow meter can measure the flow of the conductive fluid. The electromagnetic flow meter can only measure the flow of conductive liquid, so there must be a lining inside.