US Patent 6910392 Bending beam load cell with torque sensitivity compensation

A bending beam load cell can be compensated for side-to-side off center load sensitivity by simple electrical adjustments if a pair of shear sensing strain gages are bonded to each bending beam midway between axial strain gages used to measure bending strains. The shear sensing strain gages measure torque on the load cell, and are incorporated in bridge circuits that make it possible to vary the amount of torque sensitivity correction by changing the value of a trimming resistor. The bridge circuits also include circuit components for compensation of front-to-back off center load error and for zero adjustment. Four strain gages on each bending beam can be part of a single composite strain gage element, so the shear sensing strain gages do not add any cost to the load cell. Such a load cell can also be hermetically sealed before any compensation of offset load errors is done.