So, what's a magmeter?

A magmeter, or more precisely, an electromagnetic flowmeter, is a device to measure the flow of conductive liquids in pipes by using Faraday's principle of magnetic induction (hence: magmeter). In short, it states that a conductor (water) moving through a magnetic field (produced by the sensor our flowmeter) will induce an electric current proportional to the velocity of the liquid (measured by our flowmeter). Now, if you know the velocity of the flow and the diameter of the pipe you can calculate flow.

Sounds simple enough, but there is a little more to it then you might think. Faraday himself realized the potential for measurement when he attempted to measure the flow of the river Thames with a device suspended from a bridge. Unfortunately his 19th century equipment was not up to the task of detecting the relatively minuscule current generated by his device. Traditionally magmeters were simply pieces of pipe, of the same size as the pipe to be measured, wrapped in copper wire. The electrodes, meant to pick up the induced current, were mounted opposite each other on the inside of the pipe and connected to various more or less successfully devices on the outside world intended to "process data", as we would call it today. Of course there were drawbacks with this technology too numerous to mention. The larger the pipe the larger the magmeter had to be, accompanied by escalating costs to purchase (about $ 1000.00 per inch) and to install. In some of the bigger pipes, cranes and whole work crews were required to install, never mind service or repair these monsters. For obvious logistical reasons once installed most magmeters of this type were set in stone.

Operating one such flowmeter was quite another matter. Proper energizing of the coil was always a challenge, as the miles and miles of copper wire would swallow enough electricity to light a small town. The argument has always been that such in-line magmeters had an advantage since the whole of the flow in the pipe contributes to the measurement. The problem with this, of course, is that distance from the electrodes, particularly in the larger pipes does very much influence the contribution from different portions of the flow. Much of the current induced in such larger pipes originates from the flow very close to the electrodes. In other words the much slower flow near the pipe wall contributes to the overall result in a disproportional amount. The proximity of the electrodes to the pipe wall also contributes to the problems caused by coating, more likely with some liquids then with others.

Already in 1936 Alexander Collin of Columbia University, New York, recognized and published on the advantages of using a sensor type of magnetic measurement in which the electrodes were exposed to the much higher flows away from the pipe wall towards the center of the pipe. Since then the idea of a sensor-style electromagnetic flowmeter has been taken up by numerous manufacturers of such devices. In their approach they can be roughly divided into three distinct categories.

The first group originally built in-line magmeters and was in some respects forced by the market to embrace this new technology. Yet they are still reluctant to give their sensor style devices equal billing to their in-line products for fear of undercutting and de-stabilizing their own market. Although in potentially superior to any in-line mag the much cheaper sensor magmeter could potentially kill their traditional in-line magmeter profits. You will rarely find this type company promoting the sensor style magmeter with much conviction, but rather selling it as a second rate, temporary or cheap alternative to the real thing; namely the much more profitable and well established in-line mag.

The second category of sensor style magmeter manufacturers have adopted variations on the theme of cheap mass production. Being essentially a one-size-fits-all technology the sensor style magmeter at first glance lends itself to mass production. Although able to offer a seemingly sophisticated technology at an "affordable price", this inevitably leads to compromises in the quality of the product. Mass production requires a stable product and is reluctant to permit frequent changes or improvements. Therefore mass production can lead to stagnation. As a result 10 or 20 year lag in the state of technology is not an infrequent occurrence. Many have attempted to compensate by adding recent technology to the data processing components of their instruments, but that has done little to alleviate the basic shortcomings of the hardware. The ability to perform, in this technology as in any other is very much a matter of the basic hardware and how it can be improved. It does indeed take more than a coil, two electrodes, tradition or extravagant claims to make a magmeter. Thanks to these proponents of the technology it has been relegated still too often to a secondary role. Customers traditionally reluctant to try new things have not been impressed and convinced. But there is yet hope for the sensor.

Finally, only the third type of manufacturer takes the technology seriously. Quality is the most important aspect, in having this attitude reciprocated by the customer. Research and development and constant improvements are an integral part of this approach to measurement.

MSR Magmeter believes in quality above all. We will not produce a flowmeter unless we have the best materials available. We will not sell a flowmeter unless we can expect the customer to be completely satisfied. We will not ship a flowmeter until it is thoroughly tested and we are certain that it will perform as promised in all respects. Find out more about the latest version of Magnum and we are certain you will not find anything better on the market today, no matter what its claims are.

If you have any questions or problems relating to flow measurement please drop us a line. Perhaps we can help.

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