E008 - Extraneous Force Immunity
Great care must be taken to ensure force transmission is achieved with correct alignment to the loadcell’s intended sensing axis and the components forming the load path. Refer to sheet E005: Force Alignment. However in many circumstances the need to measure the component of a vector requires the loadcell to perform accurate measurements whilst under the influence of a force component perpendicular to the axis of the desired measurement.
We can design into loadcells a degree of immunity to extraneous forces. In essence this is how we can produce multi-axis loadcells with pure outputs where the degree of EFI (Extraneous Force Immunity) is quantified by the cross talk between the measurement axes. Refer to sheet E009: Cross talk.
Some simple generic designs are inherently immune to lateral force components, e.g. the F254. We do not normally quantify this immunity but when requested are able to carry out multi-axis vector force applications enabling this information to be provided. Measurements made on our multi-axis verification rig have uncertainties slightly higher than our normal calibration rigs.
Often extraneous forces are variable, in these cases we recommend the use of two or three axis loadcells.
Whenever loads are not colinearly aligned through a load path to the loadcell the details should be discussed with our engineering department.