Column Load Cells and Tension Links: Measurement of Force, Torque, and other Variables

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Column Load Cells and Tension Links

In some cases, the physical arrangement of the mechanical system where a load measurement must be made does not readily lend itself to the introduction of a bending beam transducer. In others, the required mechanical connections for load transfer to the transducer may dictate a different form of spring element. Such problems can sometimes be overcome with an axially loaded straight metal bar as the spring element. Because the stress in the bar is uniformly distributed over the cross section (except near the ends), and because the bar can usually be made quite short, this form of spring element is inherently much lower in compliance than a cantilever beam of similar size and design strain level. As a result of its low sensitivity in terms of strain versus load, the axially loaded spring design is best suited for the measurement of very large loads (in excess of, say, 10000 lb or 5000 kg).

A direct-stress spring element can be loaded, of course, either in compression as a column or in tension to form what is sometimes called a "tension link". Since the design considerations for the two cases are basically the same with respect to transducer characteristics, no distinction is made here. Obviously, the end fittings for transmitting the load and its reaction to the spring element will differ; and, for compression loading, the column length and cross section must be proportioned to avoid any instability from buckling.