The rise of piezoelectric technology is based on several inherentadvantages . The high elastic moduli of many piezoelectric materials are comparable to those of many metals, ranging up to 10 5 N/mm². Although piezoelectric sensors are electromechanical systems that respond to pressure, the sensing elements exhibit almost no deformation (typically, the sensing elements are compressed by only a few micrometers).
This is one reason for the robustness of piezoelectric sensors, their very high natural frequency and excellent linearity even under difficult operating conditions. Furthermore, piezoelectric technology is insensitive to electromagnetic fields and radiation. Some of the materials used—particularly gallium phosphate and tourmaline —exhibit excellent stability over wide temperature ranges, enabling piezoelectric sensors to operate at temperatures up to almost 1000°C. In addition to the piezoelectric effect, tourmaline exhibits the pyroelectric effect. This effect also occurs in all piezoceramics (e.g., PZT ).
One disadvantage of piezoelectric sensors is their poor suitability for purely static measurements. A static force leads to a defined amount of charge on the surface of the piezoelectric material. If this charge is measured not with a charge amplifier , but rather—technically incorrectly—with an impedance converter , charges are continuously lost, ultimately leading to a continuous signal drop. Elevated temperatures cause an additional drop in internal resistance ; therefore, only materials with a high internal resistance can be used for such measurement conditions.
It would be wrong to assume that piezoelectric sensors can only be used for very fast processes or under moderate conditions. There are numerous applications where measurements are taken under quasi-static conditions, as well as sensors for pressure measurements above 500 °C.
