How to interpret deflection of loadcells for overload protection?
The ability to weigh with a load cell depends primarily on its ability to deflect / bend repeatably when load is applied or removed.
Mechanical stops for load cells
Mechanical stops are mainly used for bending beam, shear beam and single point load cells because they have a relatively high strain level with greater deflections compared with other measuring principles. A mechanical stop or overload protection can be simply achieved by installing a screw under the loadcell.
Where should the mechanical stop be installed?
If you contact your sales representative at Zemic Europe we are able to specify the deflection at eMax / full scale. This specification is calculated by the use of a stress analysis software program. This program calculates the deflection of the load cell and gives us the deflection in tenths of mm's.
However in practice, this value is an indication. The exact deflection in tenths of mm at eMax, depends on various factors affecting the deflection values. For example; how is the force introduction installed, is the center of the scale installed exactly above the center of the loadcell etc.
The correct way to determine the distance to the screw is to load your application to a 110% full scale situation. When the application is loaded install the screw in such a way that the screw is touching the loadcell. Remove the weight and the mechanical overload protection has been installed properly.
The ability to weigh with a load cell depends primarily on its ability to deflect repeatably when load is applied or removed.