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4 - Load Cell Geometry
There are two predominant geometries for load cell systems: compression (vertical) and shear beam (horizontal).
Compression load cells Compression load cells (analog and digital) measure loading with strain gauges on vertical columns run- ning through the center of the load cell. Typically, those load cells are used in a “rocker pin” design, allowing the weighbridge a small amount of free movement within the restraints of a checking system. That checking system can include shock-absorbing bumpers, adjustable bolts and check rods. When adjusted correctly, the system allows just enough movement that the weighbridge and load cells are self-centering. That pre- vents the scale from binding on the foundation or approaches. It also limits the opportunities for physical wear to the components. The rocker pin design should also include anti-rotation features so that the load cells cannot rotate in their positions. Shear beam and double-ended shear-beam Shear beam and double-ended shear-beam (including cantilever) load cells also use strain gauges, except they are mounted to a horizontal beam. Single-ended shear beams are fixed on one end and linked to the weighbridge on the other. Double-ended shear beams are typically fixed or supported in the center and linked to the weighbridge on both ends. Either way, those beams typically are linked to a lower mounting point on the weighbridge, creating a suspension system. There, the weighbridge is able to swing slightly in two or more directions. That system is designed to be self-centering, thanks to the gravitational pull down- ward on the beam ends. However, the links between the beam ends and the scale structure should be regu- larly inspected for signs of wear.
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