Electromagnetic Flow Meter
Electromagnetic flow meters, also known as magnetic flow meters, mag meters, or even electromags, are a type of volumetric flow meter. They determine flow rate using a magnetic field that is applied directly to the metering tube. This magnetic field creates a potential difference that is proportional to the velocity of the fluid flow inside the tube, perpendicular to the flux lines. The meters measure this difference in order to get the flow rate. They do so using sensing electrodes that applied to the magnetic field in such a way that they are aligned perpendicularly to the flow.
One way to understand the way that electromagnetic flow meters work is by considering Faraday's Law of electromagnetic induction. Faraday's Law states that, as it moves at right angles through a magnetic field, the voltage produced by a conductor is proportional to its (the conductor's) velocity. In flow meter terms: electromagnetic flow meters use signal voltage in order to determine velocity, where the flow rate of the conductor is the fluid. For this reason, it is essential that the fluid used with electromagnetic flow meters is conductive and water based. In addition, the pipe in which the fluid flows must have a nonconducting liner. The electrodes must not be allowed to corrode.
These flow meters only work with conductive and water-based fluids. They're ideal for measuring flow rate of dirty liquids. However, they can work with a wide range of fluids; in fact, they are widely considered the third most common type of flow meter. This is largely due to the fact that they have no moving parts, which means that they require less maintenance, and tend to last longer.
Because electromagnetic flow meters can only be used with conductive, water-based fluids, before making the decision to purchase one, ask yourself the following questions about your application: Does my application used conductive fluid? Is my application fluid abrasive? What is the minimum and maximum flow rate of my application? Is my pipe always full?
Even if you ask yourself all the right questions, the only way to know without a doubt that this type of flow meter is right for you is by talking over your application with an experienced flow meter manufacturer. In fact, a good manufacturer, like one of those we have listed on this site, will be able to provide you with a custom flow meter, if you wish.