All the techniques and standards listed have been developed for the calibration of systems to measure static forces acting along a single well-defined axis. But calibrations are also required for multi-axis situations and for systems which measure non-static (dynamic) forces.

Multi-axis calibration

Multi-axis calibration is similar to single axis calibration but done once for each axis. The calibration of multi-component force sensors is more demanding on the equipment, although the principles remain the same. Measurement of cross talk requires some new considerations. Cross talk is the effect of a calibration force applied along one axis on a different component, for example an output on the x-axis transducer caused by a y-component force. To measure cross talk of 0.1 % with a maximum uncertainty of ±0.01 % requires a force alignment to a perfectly perpendicular theoretical angle of less than 20', illustrating the need for special test machines.

Dynamic force calibration

There are very few sources of traceable dynamic force calibration – and certainly none in the force and frequency ranges measured by the majority of commercially available dynamic force transducers. In the absence of suitable standards and procedures, the statically-derived force transducer sensitivities are generally assumed to be applicable to dynamic force measurements, perhaps after modification to take account of a theoretical model. The dynamic behaviour (natural frequency) of load washers or dynamometers, for example, depends very much on the stiffness and mass of the structure housing the sensor.

This is not  a satisfactory situation but, pending the development of suitable standards, purchasers should bear in mind the complexities and difficulties of both specifying dynamic sensors and interpreting the results they yield.