Electromagnetic flow meter is a commonly used flow meter in industrial measurement. Because of its wide application, customers often ask questions encountered during use. Here we will talk about the solution to the problem of large bubbles in the fluid when the electromagnetic flow meter measures liquid. Some customers mentioned why electromagnetic flow meter are equipped with linings. We will answer this question based on the principles of electromagnetic flow meter.

  There will be many bubbles in the electromagnetic flow meter when measuring liquid, which often leads to errors in the flow meter measurement and affects its use. 
Generally, the fluid measured by the electromagnetic flow meter will contain some bubbles. If these bubbles are distributed evenly, they will not affect the measurement. However, once the bubbles become larger, they can cover the entire electrode when they rub against the electrode, causing the flow signal input loop to instantly open, causing the output signal to shake.

  How to determine whether the measurement error of the electromagnetic flow meter is caused by bubbles in the liquid being measured? How to deal with this situation? Let's briefly introduce it. 
When the measurement results shake, 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 determining that a large number of bubbles affect the measurement results of the electromagnetic flow meter, relevant solutions must be found. If it is judged that the installation position causes a large number of bubbles to merge into the liquid, for example, the electromagnetic flow meter is installed at a high point in the piping system and stores gas or the outside air is sucked in to cause the flow meter to shake. Changing the installation position is the most effective solution. However, in many applications where the diameter is large or the installation position is difficult to change, it is recommended to install a gas collection bag and an exhaust valve upstream of the electromagnetic flow meter to eliminate excess gas, reduce factors affecting the measurement results, and ensure accurate measurement.

Regarding why electromagnetic flow meter need to be lined, it starts with the principle of electromagnetic flow meter. An electromagnetic flow meter generally has 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 generate an electromotive force proportional to the speed. The function of the electrode is to measure this induced electromotive force. Therefore, only the electrodes in the measuring tube are connected to the conductive liquid. The other parts are lined. Insulation must be ensured so that the electromagnetic flow meter can work normally. If the metal pipe with a magnetic field is also in contact with the liquid, and there is a short circuit between the conductive liquid measured by the electromagnetic flow meter and the metal pipe, there will be conduction, and the potential will be conducted away, making the electromagnetic flow meter unable to measure the potential. Therefore, the inside of the electromagnetic flow meter is lined.

  When measuring flow, the conductive liquid flows through a magnetic field perpendicular to the flow direction at a speed V. The flow of the conductive liquid induces a voltage proportional to the average flow rate. The induced voltage signal is picked up through two or more electrodes in direct contact with the liquid and sent to the converter through a cable for intelligent processing. Then the LCD displays or converts it into a standard signal of 4~20ma and 0-1khz for output. In this way, the electromagnetic flow meter can measure the flow rate of conductive fluid. Electromagnetic flow meter can only measure the flow of conductive liquids, so they must be lined inside.