- High Performance Achieved Through Dual Frequency Excitation -

Yokogawa Electric Corporation announces the release of the ADMAG AXR, a two-wire magnetic flowmeter that achieves high performance by using the dual frequency excitation method, a world first. (See attached reference materials.) Until now, Yokogawa has offered only four-wire magnetic flowmeters with excellent functionality. By adding to its line-up a new two-wire magnetic flowmeter that simultaneously achieves high performance and low installation and running costs, Yokogawa aims to take the top share of the global magnetic flowmeter market. This product is scheduled for release in February 2009.

Background of Development

Magnetic flowmeters are used to measure the flow rate of conductive fluids such as water and chemicals. Most are of the four-wire type, which achieves high accuracy and performance by means of a dedicated power supply cable that is separate from the signal cable used for current output. In contrast, the two-wire type uses just one pair of wires for current output and power supply. As two-wire magnetic flowmeters require neither a dedicated power supply cable nor a power supply unit, their installation costs are significantly lower. However, conventional two-wire magnetic flowmeters have not met the process automation field's minimum performance requirements in such areas as measurement accuracy and stability, which explains why they have not been well accepted in the marketplace. As many companies now need to reduce their instrumentation costs, flowmeter suppliers are being called upon to develop products such as high-performance two-wire magnetic flowmeters

In response to this need, Yokogawa has developed a technology that can minimize electric noise in two-wire models to a level comparable to that of four-wire magnetic flowmeters, thereby achieving high measurement accuracy and stability.

The Magnetic Flowmeter Market

Global sales of magnetic flowmeters totaled US$730 million in 2006 and are projected to reach US$870 million by 2011, a 20% increase. This can be attributed to infrastructure building in emerging markets and a steady increase in capital investment centering on chemical, pharmaceutical, and electric power plants*1. Although two-wire magnetic flowmeters have accounted for only a small share of the world magnetic flowmeter market because of performance concerns, the availability of this high-performance two-wire model means that there is now significant opportunity for growth.

Yokogawa is one of the top suppliers of magnetic flowmeters in the global market, with a 12% share*1. By launching this new product, Yokogawa aims to take an 18% share by 2010.

*1 Source: Magnetic Flowmeter Worldwide Outlook, Market Analysis and Forecast Through 2011, a study published by the ARC Advisory Group on February 5, 2007

Product Features

1. Dual frequency excitation
This two-wire magnetic flowmeter uses the dual frequency excitation method, giving it the high measurement accuracy, stability, and reliability required for use in control loops. The dual frequency excitation method is useful for improving stability, but power consumption is increased by the need to execute complex algorithms. It would not have been possible to adopt the dual frequency excitation method in a two-wire magnetic flowmeter without the development of new technology that made it possible to have both high performance and very low power consumption. Yokogawa developed and introduced this technology in this new two-wire magnetic flowmeter.

2. New coil construction method and low-noise technology
Because a two-wire magnetic flowmeter has a limited power supply capability, the current supplied to the excitation coil is too weak for signals to be differentiated from electrical noise. To resolve this problem, Yokogawa adopted a new high density coil construction method that enables a stronger magnetic field to be generated with a low current. Yokogawa has also found ways to minimize the noise level by smoothing the inner surface of the measuring tube and developing an electrode that generates very little noise. Through these efforts, it has successfully resolved the problem of differentiating signals from electrical noise and has achieved a measurement accuracy that is comparable to the four-wire type.

3. Ease of use
User friendliness has been enhanced through the addition of a full dot-matrix LCD capable of displaying messages in six different languages, enabling magnet switches to be operated without opening the cover, the addition of an electrode adhesion diagnosis function, and a design change that allows the orientation of the converter to be changed on site.

4. Reduced installation and running costs
The elimination of the need for a dedicated power supply unit and power supply cable has enabled a sharp reduction in instrumentation cost. The lower power consumption of this two-wire instrument also reduces running costs.

Major Target Markets
A wide range of industries such as chemicals, iron & steel, and food & beverages

Applications

Fluid flow measurement

- Reference -

Magnetic flowmeter operating principle

The operation of a magnetic flowmeter is based on Faraday's Law, which states that when conductive fluids pass through a magnetic field they generate electromotive force in proportion to flow velocity. The electromotive force is generated in a direction perpendicular to the direction of the fluid motion and the magnetic field, according to Fleming's Right-hand Rule.

The magnetic flowmeter detects this electromotive force by using a pair of electrodes installed inside the measuring tube, calculates the flow rate, converts it to 4-20 mA and pulse signals, and outputs them. It is one of the most accurate industrial flowmeter types. It has no movable parts or other obstructions inside the measuring tube, can be used with corrosive fluids, and is maintenance-free. Magnetic flowmeters are therefore extensively used in such industries as chemicals, food, iron & steel, pulp & paper, and water supply.

Features of dual frequency excitation method
The dual frequency excitation method is a Yokogawa innovation. With this method, a magnetic field is generated (excitation) by supplying a current with two high and low frequency components through the flowmeter coil. Having both the advantages of low frequency excitation (stability) and high frequency excitation (noise resistance), this method offers greater accuracy and stability than the single frequency excitation method.

Courtesy of Yokogawa