Pressductor® at 70: continuing to deliver
04/06/2025 ABB Process Automation
It’s often said that some of the best inventions are also some of the simplest. With its straightforward design featuring a steel block with four holes and two windings of copper, ABB’s Pressductor® has become the device of choice for measuring force and torque in a range of industrial applications since its original launch in 1954. Daniel Jonsson, Global Product Line Manager - Rolling Mill Products and Web Tension for ABB explains why.
Since its arrival in industry 70 years ago, Pressductor sensor technology has been helping to deliver unrivalled manufacturing quality, thanks to its unique ability to provide accurate, stable measurement of force, tension, pressure and torque under the most arduous industrial conditions. Today, this technology is continuing to deliver new benefits, providing vast amounts of data from which ever more manufacturing knowledge can be gleaned.
Pressductor transducers can already be found virtually anywhere that produces flexible strip or webs, regardless of whether the materials being produced are metals, paper or plastics. New applications are still emerging, with the technology’s established track record in metals and paper now seeing Pressductor® being adopted by the fast-growing battery industry, for example.
Whatever products these materials are destined for, consumers and businesses expect them to be flawlessly smooth, consistent and of uniform thickness. It may sound simple, but it was a tricky proposition until the arrival of magnetoelastic technology in the 1950s.
Over the years, other technologies have evolved for the measurement of force, tension and torque in industrial applications, but these competing approaches have one drawback in common. They all rely on movement – essentially bending or stretching the measurement elements to produce a signal. That leaves them vulnerable under challenging operating conditions
Magnetoelastic technology
In 1954, Dr. Orvar Dahle and his wife Birgit were the first to patent the concept of using the magnetoelastic effect to measure force and torque. Orvar and Birgit were both researchers at Asea, which later became part of Asea Brown Boveri (ABB). The first instruments to hit the market using the Dahle’s new approach were a torque sensor, Torductor®, and a force sensor, Pressductor.
Rather than relying on physical movement, magnetoelastic technology relies on the magnetic properties of certain steels to alter their magnetic field in response to the force applied.
Today’s Pressductor transducers contain two perpendicular windings of copper wire running through four holes of a steel block. A current is applied to generate a magnetic field in one of the windings. When the transducer experiences a mechanical force, the magnetoelastic property of the steel alters the magnetic field pattern, inducing an AC voltage in the second coil that is proportional to the force.
The measurement signal is exceptionally strong, which means that magnetoelastic transducers are more resilient than alternative technologies to the influence of electrical interference – whether from induced currents in the signal cabling or other wireless devices.
This technology also copes naturally with overloads of 1,000 percent of the cell capacity, depending on the type of load cell, while the deflection under typical industrial loads is roughly between 10 and 100 times less than the displacement typically experienced with movement-based devices. This makes the Pressductor more or less impervious to the kind of overloads and shocks that could throw the calibration off or even destroy other instruments, such as strain gauges.
Pressductor gauges are also able to cope with the everyday vibrations and temperature variations associated with harsh industrial operations.
How did we get here?
Marking a step change in accuracy and stability, it’s no wonder that the arrival of the first commercial Pressductor roll force meter in 1954 sparked a revolution in the measurement of force, tension, pressure and torque in harsh environments.
When the Dahles were granted their patent, global production of steel was about 200 million tonnes a year. By 1970, some 15 years later, it had tripled. Pressductor clearly arrived at the right time to support this expansion.
Since then, ABB has launched an entire family of instruments based on the same underlying magnetoelastic phenomenon. These have evolved to cover applications such as strip/web tension measurement, weighing, torque measurement and flatness measurement and control. This adaptability has seen the technology crop up in some wide-ranging applications over the intervening years, such as monitoring the torque on large ships’ propellers, weighing molten steel, ensuring that the supports for North Sea oil rigs are welded together properly, printing newspapers in Oslo, manufacturing the soft fibers for baby’s diapers, optimizing flatness in aluminum and battery production, and helping to extend the life of London’s iconic Tower Bridge.
But it’s in the metals industry where these instruments have been most widely used, particularly in flat rolling mills, where they have been extremely successful. The Stressometer®, for instance, is the predominant flatness system across the world’s cold rolling mills. It’s used for metals from carbon steel and stainless steel to copper and aluminum, dealing with thicknesses of up to 12 millimeters. It can measure flatness in foil with a thickness of a few thousandths of a millimeter.
With costs exceeding $500 per ton for steel, $2,500 per ton for aluminum and stainless steel and $4,000 per ton for copper, it is essential to ensure that every ton of sheet metal produced meets the highest quality standards. For this reason, effective surface finish and flatness control is business-critical. A ‘right first time’ approach to production also reduces the rework and waste associated with faulty products, helping companies to minimize energy consumption and any associated emissions in line with sustainability goals. With iron and steel alone accounting for more than 10% of industrial energy consumption in the EU, according to the latest available figures, the potential impact is significant.
One of the more recent milestones in Stressometer’s history has been the introduction of its Digital Transmission Unit (DTU), which was launched in 2014. The unit makes it possible to contactlessly transmit measurement signals from a Stressometer® roll, as well as contactlessly supply sensors with power. The DTU’s introduction has meant that the need for maintenance has been eliminated.
Future trends
What does the future hold for Stressometer and other ABB systems based on Pressductor technology? First, demand for rolled products is set to remain strong. Standards of living are improving in many parts of the world, resulting in increased demand for consumer products such as vehicles and white goods. These products depend on rolled products and thus measurement and control of roll force, strip thickness, tension and flatness.
At the same time, there are a lot of old rolling mills in operation. To remain competitive, they will need to modernize or rebuild to comply with increasingly stringent environmental requirements. With their ability to improve accuracy and reduce off-specification product, waste and reworking, ABB solutions can help operators upgrade and optimize production to boost quality, optimize costs and achieve their environmental goals.
Meanwhile, technological developments in electronics and software are proceeding at great speed. Cloud solutions, learning systems and AI are becoming increasingly important. Combining these trends with ever-growing use of automation, it becomes clear that all forms of manufacturing will demand increasingly precise measurement data and analyses of that data. These are demands that Pressductor technology, which is already at the cutting edge of flatness process optimization, is well equipped to meet.
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ABB Process Automation (ABB Instrumentation)
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Web: https://new.abb.com/about/our-businesses/process-automation
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