![]() ![]() Most of these sensors are intended for measuring internal strain, longitudinal or transverse, and are designed as so-called strain pins to be inserted in a bore. They have the important advantage over strain gauges that they are very well suited for dynamical measurements. Piezoelectric strain sensors can be seen as force sensors with a design that emphasizes strain. Reaction torque sensors may also rely on the piezoelectric effect, using several shear-mode piezoelectric elements, whereas torque measurements on rotating shafts typically are done with strain gauges. The bimorph element consists of two piezoelectric plates, either poled in opposite directions (series configuration) or in the same direction (parallel configuration). Where d 33 is the piezoelectric charge coefficient.Īlternatively, a flexure mode design may be used for certain piezoelectric sensors, in which case a so-called bimorph element within the sensor is deflected by the input force. For a poled piezoelectric ceramic, the charge Q is proportional to the input force F according to the following equation It follows directly from the basic piezoelectric equations that a piezoelectric element will produce a charge when a force is applied parallel to the direction of polarization. Sensors for force, torque, strain and pressure The upper frequency limit is generally given by the natural frequency of the piezoelectric sensor, which in turn is determined by the design. As a rule of thumb, 10 Hz can be considered as the minimum frequency for piezoelectric ceramics. Typically, such piezoelectric sensors are less suitable for low-frequency signals due to charge dissipation. Through the direct piezoelectric effect, several mechanical quantities can be measured, including force and torque, strain, pressure, acceleration and acoustic emission. Sensors using the direct piezoelectric effect ![]() While the majority of piezoelectric sensors are based on the direct effect, some also exploit the converse effect as is the case with resonant piezoelectric sensors. Piezoelectric sensors utilize the direct piezoelectric effect to convert a mechanical input into an electric signal. ![]()
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