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| | | Piezoelectric Measuring Technology | | |
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| | | Transverse Effect In the case of transversal effect, a force Fy in the direction of one of the neutral axes y produces a charge on the surfaces of the corresponding polar axis x. In contrast to the longitudinal piezoelectric effect the magnitude of this charge, which occurs on unloaded surfaces, is dependent on the geometrical dimensions of the piezoelectric element. Assuming element dimensions a and b, the charge is: Qy — dn * Fy * b/a Thus, the transversal effect makes it possible to obtain a greater charge by suitable shaping and alignment of the piezoelectric elements. Elements with a transversal effect can be used for high-sensitivity pressure, strain and force sensors. | | |
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| | | | | | | | | | | | Possible cutting angles in the quartz element | | | | | Transverse cut | | | | | Polystable cut ) | < | | | | | | | N | | | | | | y | | Shear cut | | | | | | | | | | | |
| | | The quartz crystal produces a charge signal which is proportional to the acting force. Due to the high rigidity of the crystal, the corresponding measuring deflection is low, mostly in the range of several millimeters. The high natural frequency of the quartz element is beneficial for measuring fast and dynamic processes. Due to the minimum measuring deflection, measurement of slow, quasi-static processes will produce minimum measuring errors. | | |
| | | Quartz as a Piezoelectric Material Piezoelectric materials for sensor elements must exhibit a very high mechanical strength and rigidity. Another requirement is the stability of the mechanical and electrical properties across a wide temperature range and for long service periods. Moreover, they should provide a high sensitivity, good linearity, negligible hysteresis (i.e. the rising and falling calibration curves are identical) and a high electrical insulation resistance. | | |
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| | | Quartz sensors are extraordinarily stable, sturdy and compact. Therefore they are not only used for research and development, but are also widely used for industrial production and testing processes. | | |
| | | Quartz meets all of these requirements and is therefore ideal for sensors. It can be produced synthetically and exhibits other qualities, which are beneficial for measurement. A synthetic quartz element, for example, can be used in temperatures of up to 400 °C. Quartz can be cut in different angles to exhibit sensitivity to pressure or shear forces, depending on which of the three piezoelectric effects is to be used. | | |
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