Electromagnetic flowmeter is a commonly used flow meter in industrial measurement. Because of its wide application, customers often raise problems encountered during use.

Electromagnetic flowmeter is a commonly used flow meter in industrial measurement. Because of its wide application, customers often raise problems encountered during use. Here we will talk about the solution to the large bubbles in the fluid when the electromagnetic flowmeter measures the liquid. Some customers also mentioned why electromagnetic flowmeters are equipped with inner linings. We will answer this question from the principle of electromagnetic flowmeters.

Electromagnetic flowmeters will have a lot of bubbles in the process of measuring liquids, which often leads to errors in flowmeter measurement and affects use.
Generally, the fluid measured by the electromagnetic flowmeter will contain some air bubbles, and if the air bubbles are evenly distributed, it will not affect the measurement. The signal input circuit is opened instantaneously, causing the output signal to fluctuate.

 

How to judge that the measurement error of the electromagnetic flowmeter is caused by the air bubbles in the measured liquid? How to deal with this situation? Let's briefly introduce it.
When the measurement result shakes, immediately cut off the excitation circuit current of the magnetic field. If the instrument still displays and is unstable at this time, it means that it is mostly caused by the influence of bubbles.


After confirming that a large number of air bubbles affect the measurement results of the electromagnetic flowmeter, it is necessary to find relevant solutions. If it is judged that a large number of air bubbles are integrated into the liquid due to the installation location, such as the electromagnetic flowmeter is installed at a high point of the piping system and stores gas or is inhaled from the outside. If the air causes the flowmeter to shake, changing the installation location is the most effective solution. However, in many applications, the caliber is large or the installation location is not easy to change. It is recommended to install an air collection bag and an exhaust valve upstream of the electromagnetic flowmeter to remove excess gas. , to reduce the influence factors on the measurement results, to ensure the accuracy of the measurement.

As for why the electromagnetic flowmeter should be lined, it starts with the principle of the electromagnetic flowmeter. Electromagnetic flowmeters generally have a set of coils and two electrodes. The function of the coils 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 force line, a corresponding force proportional to the speed will be generated. The electromotive force of the electrode is to measure the induced electromotive force, so only the electrode in the measuring tube is connected to the conductive liquid, and the other parts are the inner lining. The electromagnetic flowmeter can work normally only if the insulation is ensured. If the metal pipe with the magnetic field is also in contact with the liquid, there will be a short circuit between the conductive liquid measured by the electromagnetic flowmeter and the metal pipe, and there will be conduction, which will lead away the potential so that the electromagnetic flowmeter cannot measure the potential. Therefore, the inside of the electromagnetic flowmeter is lined.

When measuring the flow rate, the conductive liquid flows through a magnetic field perpendicular to the flow direction at a velocity V, and the flow of the conductive liquid induces a voltage proportional to the average flow rate, and the induced voltage signal passes through two or more channels directly connected to the liquid. The contacted electrodes are picked out and sent to the converter through the cable for intelligent processing, and then LCD display or conversion into standard signal 4-20ma and 0-1khz output. In this way, the electromagnetic flowmeter can measure the flow of the conductive fluid. Electromagnetic flowmeters can only measure the flow of conductive liquids, so they must be lined inside.