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New Mass-View Is High Tech Replacement For VA Meters

Posted: Tuesday 1st April 2008

Bronkhorst High-Tech, European market leader in thermal mass flow metering and control instrumentation, has developed a no-nonsense, digital alternative to the conventional VA meter (variable area meter) or rotameter, a design that dates back to the 19th century.

Employing the latest OLED (organic light emitting diode) technology, as used in mobile phones and MP3 players, the new Mass-View® flow meter series incorporates a digital bar graph of actual gas flow, which is clearly visible from all angles, as well as indicating flow units, fluid type and totalised figures. Also available with an optional in-built needle valve for flow control duties, it is designed to mimic the straightforward features and vertical format of the VA meter, but with the considerable added benefits of an electronic output signal, measuring accuracy as high as ± 0.5%, virtual independence from gas temperature and pressure variations, freedom from parallax error and inherently safe construction, with no fragile glass components in the flow path.

For many industrial processes and chemical plants, Bronkhorst’s new Mass-View will eliminate the relative inaccuracy of VA meters, the need to recalibrate for different gases and the safety risk of ruptured glass tubes, at a price directly comparable with the cost of a variable area meter and separate transmitter. For OEMs, it offers the option of incorporating more modern, aesthetic gas flow measuring instruments into their equipment, presenting a more appropriate, high technology image.

Still commanding a high proportion of the industrial flowmeter market, with around a million installed annually, the variable area meter is one of the oldest technologies available. It typically comprises a tapered vertical tube, usually made of glass or plastic, and a metering float, which is free to move within the tube; fluid flow causes the float to rise, with the height providing an indication of flow rate and the tube graduated in appropriate flow units.

The basic advantages of the VA meter are its relatively low cost, reasonable accuracy, simplicity of design, low maintenance and ease of installation. However, one drawback is that flowmeter accuracy degrades when fluid temperatures and pressures fluctuate, whilst there is also a problem of parallax error when taking readings from different viewpoints. In addition, glass and plastic tubes often break in usage, leading to the risk of potentially dangerous gases leaking from the instrument; to compensate, metal tubes and magnetic float sensing are sometimes used instead, but such designs are comparatively expensive, typically double the price.

Bronkhorst felt there was scope for a more high tech alternative to VA meters, employing similarly straightforward visual indication, although measuring mass flow instead of volume. Thus the Mass-View series operates on the principle of direct thermal mass flow measurement, with no by-pass for potential blockages, and requires no correction for temperature and pressure. It offers a standard accuracy rating of ± 1% FS across the range, with a high performance option improving this to ± 0.5%, flow ratings from 100 sccm to 200 SLM, and handles pressures up to 150 psi (10 bar), or higher on request. Power consumption is low and mechanical process connections are fitted for straightforward VA meter replacement.

The Mass-View incorporates the latest OLED technology, which gives a brighter readout than LCDs, can be viewed from virtually any angle and has fast signal response times. The resulting graphical OLED display is clearly visible in all conditions, with no scope for misinterpretation, and, in addition to a simple bar graph indicating current status, it offers a variety of flow readings, including totalisation. Options are accessed via a user-friendly menu, using a 4-way navigation button mounted on the front plate. An electronic output signal enables data logging against various parameters and full accountability of gas flow, such as for shared ring main applications.

Further enquiries to Bronkhorst UK, Cathrine House, London Road, Sawston CB22 3XE, tel 01223 833222

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