Advantages of piezoelectric force plates

Piezoelectric force, torque and strain sensors are very compact and rigid, and offer a measuring range of up to six decades, a high natural frequency and low interference sensitivity. They cover a wide temperature range, are overload-protected and offer long-term stability as well as freedom from fatigue. Piezoelectric sensors are ideal for almost all areas of application, particularly for the type of dynamic and highly sensitive processes encountered in biomechanics.

The operating principle of quartz crystal sensors in Kistler force plates means that compared with sensors with strain gages they offer decisive advantages, most of which are attributable to their comparatively high rigidity.

Sturdiness, overload protection and long-term stability
Piezoelectric force plates are very compact for an instrument with such a wide measuring range. Their rigidity makes them robust and gives them a high factor of safety against overload. Even after millions of load cycles and frequent thermal cycling the plates show no sign of fatigue or sensitivity drift. With correct use their service life is virtually unlimited.

High sensitivity
over wide measuring range
Unlike strain gages, quartz crystal sensors have a wide measuring range of up to six decades, as their sensitivity, threshold and resolution are not linked to the stiffness of elastically deformable structures and hence to a limited measuring range. Irrespective of the measuring range and any initial load, piezoelectric sensors can also be used to measure very small forces, such in minute variations in a large base load.

Exact zero – No offset
With piezoelectric sensors the zero is redetermined prior to each new measurement process. Resetting physically tares the sensors by discharging any electric charge generated by factors such as an initial load. This automatically eliminates the effect of all static and slowly changing boundary conditions (such as mounting position, weight of supported elements and temperature fluctuations) without affecting the measurement accuracy.

Balance analysis and static measurements
Due to their low threshold, high sensitivity and very high accuracy Kistler force plates are ideal for balance analyses and other quasistatic measurements taken over a period of several minutes. However, piezoelectric sensors are not suitable for truly static measurements over several hours or days, as charge amplifiers always exhibit a slight drift. Drift is defined as an undesirable change in output signal over a extended period of time that is not a function of the measurand. Charge amplifier drift is unavoidable because there is no material available offering infinite insulation.