Load Cell is a device that converts force into electrical signal.The majority of today's load cell designs use strain gauges(which is a device that changes resistance when it is deformed or stressed) as the sensing element, whether foil or semiconductor.A strain gauge based load cell is made of a specially engineered mechanical component called as an element. Four strain gauges are positioned precisely and bonded on to the element using a special adhesive.
Foil gauges offer the largest choice of different types and in consequence tend to be the most used in load cell designs. Strain gauge patterns offer measurement of tension, compression and shear forces.
Semiconductor strain gauges come in a smaller range of patterns but offer the advantages of being extremely small and have large gauge factors, resulting in much larger outputs for the same given stress. Due to these properties, they tend to be used for the miniature load cell designs.
The force-electrical signal conversion happens in two stages-
force applied deforms the element which in turn deforms the strain gauges
strain gauges converts the deformation to electrical signals
The strain gauges are wired in Wheatstone bridge configuration. The bridge is connected to a power supply unit and a signal conditioner through a 4-core cable. When an input voltage (10VDC) is applied to the bridge, the output is a voltage in the range of few millivolts.
The load cell output is proportional to the load applied to the element.
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