Electromagnetic flowmeters require conductive liquids, such as tap water, industrial sewage, domestic wastewater, mud, and so on.

Electromagnetic flowmeters require conductive liquids, such as tap water, industrial sewage, domestic wastewater, mud, and so on.

When measuring with the electromagnetic flowmeter, it should be noted that the liquid cannot contain bubbles, if the medium contains bubbles, it will affect the measurement results.

There are two possible causes of bubbles in a liquid; 1. External inhalation; 2. The dissolved gas (air) in the liquid is transformed into a free bubble. If the liquid contains a large bubble, it can cover the entire electrode when passing through the electrode, so that the flow signal input loop is instantly open, resulting in the output signal shaking.

Identification method: The simpler identification method is to cut off the excitation circuit current of the magnetic field when it is shaken, and if the instrument is still displayed and unstable at this time, it is mostly due to the influence of bubbles. If the electrode resistance is measured with a pointer multimeter at this time, the loop resistance to the electrode can be measured to be higher than normal. However, the test relies on long-term testing experience and data accumulated by professionals.

Solution: For the case of air in the measured medium, if it is determined to be caused by the installation position, such as because the electromagnetic flowmeter is installed at the high point of the pipe system and stored gas or external suction air caused by the flowmeter to shake, replace the installation position is the best solution, at the lowest point of the pipeline or the use of U-shaped pipe installation.

However, many applications are large caliber or installation position is not easy to change, it is recommended to install the upstream of the flow meter collector and exhaust valve, after the installation of the exhaust device, the measurement is returned to normal.