Bending Stress Measurement

Quarter-bridge System

See the figure below. If a strain gage is bonded on the surface of a rectangular section of a cantilever of which one side end is fixed and load W is applied to another side, the surface stress σ which the bonded strain gage will detect is as follows :

Strain ε is obtained by the following equation:

Half-bridge System (Adjacent-leg Bridge Connection)

As illustrated below, strain gages bonded symmetrically on the front and rear surfaces of the cantilever output positive and negative signals, respectively, with an equal absolute value. If these 2 gages are connected to adjacent legs of the bridge, the output of the bridge corresponding to the bending strain is doubled and the surface stress σ at the strain-gage bonding site is obtained by the following equation:

The adjacent-leg active half-bridge system cancels out the output of the strain gage corresponding to the force applied in the axial direction of the cantilever.