Dynamometry

Dynamometry or dynamometric methods are used to directly record reaction forces and the measured variables that can be derived from them (e.g. momentum, torques, mass moments of inertia). Knowledge of the (external) reaction forces is a prerequisite for estimating internal forces or the underlying force capacities. Today, reaction forces are usually measured electronically. Either the deformation of a measuring spring (strain gauge principle) or the charge displacement on a piezo-electric sensor is recorded via amplifiers and further processed in an evaluation computer. What all dynamometric measurement methods have in common is that changes in force are recorded as a function of time (in a force-time diagram).

Strain gauges are flat transducers or sensors that are characterized by an electrical resistance without external force. If they are deformed, this results in a change in their electrical resistance. The change in resistance is transmitted to an A/D converter via a voltage change in an electronic circuit. Today, strain gauges (e.g. from Hottinger & Baldwin) are mainly used where space is limited (e.g. on the rowing roll, ski dynamometer or horizontal bar).

The KISTLER multi-component measuring platforms, which are widely used around the world, are based on the piezo effect. The piezo effect is based on the behavior of certain crystals (especially quartz), which accumulate electrical charges at the dipoles of the crystals when (mechanical) pressure is applied. These charge displacements are first converted into electrical voltages via a charge amplifier and fed to an electronic evaluation unit.