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20 April, 2018

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Load cell senses tension horizontally

01 June, 2000

Load cell senses tension horizontally

ABB claims that it has made it easier to measure tension in web processing machines by developing a load cell that senses web tension horizontally rather than vertically. The sensor ignores the dead weight of roll assemblies and other vertical forces, which often limit the performance of conventional vertically-sensing load cells by restricting measurement of the "live load" (the web tension) to a small portion of the load cell`s capacity.

The new cell is said produce more reliable and precise tension measurements - especially in applications where machine rolls are heavy compared to the web tension - without drift in measured values or the need for recalibration after line stoppages.

Because conventional tension load cells sense forces in a vertical direction, much of their capacity is devoted to accommodating the meaningless force exerted by the weight of the roll assembly. This detracts from their performance because load cells provide their best measurement when their entire range is used to measure tension.

"The problem is not the quality of the load cells," explains Ulf Carlqvist, ABB`s design manager. "The problem occurs because these load cells are typically measuring tension with only a small portion of their rated capacity range."

ABB`s Horizontal Mini pillow-block-mounted load cell overcomes this problem by being completely insensitive to forces applied in the vertical direction. This achieved by a combination of advanced cell design and a magnetoelastic transducer technology that allows the cells to be sized according to tension level alone.

This allows users to measure tension with the full range of their load cell capacities, says Carlqvist: "They no longer have to do the equivalent of weighing a small package on a truck scale."

The load cells have the same dimensions and mount in the same way as other pillow block tension load cells. They are available in four sizes to measure web tension levels from a few kilograms up to 2,000kg.

The transducers do not need physical movement to produce the measurement signal, allowing them to be built into rugged housings, resistant to fluids, particulates, and electromagnetic interference. Machined from a solid block of stainless steel, the cells are said to eliminate the need for frequent re-calibration, re-zeroing, or replacement.




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