Piezoelectric force sensors Kistler measures dynamic forces with piezoelectric sensors. Most force sensors are provided with a spring element which deforms under load, the force applied being determined from the deformation. However, the frequency range of this type of sensor is limited by the capacity of the spring element to cope with the large deflections. To overcome this limitation, Kistler relies mainly on the piezoelectric measuring principle for the measurement of dynamic forces. Piezoelectric materials ­ quartz, for example ­ produce an electric charge proportional to the mechanical load applied: the higher the load, the higher the charge. Thus, in piezoelectric sensors, quartz serves both as the spring element and as the measuring transducer. Thanks to the high rigidity of quartz, the measuring path is very small, mostly within a range of a few microns. Where slow, quasi-static processes are being measured, this virtual absence of displacement keeps measurement error to an absolute minimum. At the other extreme, quartz ­ due to its rigidity and high natural frequency ­ has no equal in the measurement of extremely fast processes.