When crystals are exposed to pressures or forces around a particular axis, they are elastically deformed. The experience of deformation produces an electric potential, which results in the flow of an electric charge for a few seconds. The pressure acting on the sensing diaphragm generates an electrical signal, which is proportional to the amount of force and therefore to the deformation experienced by the crystal. Because the crystal can also be deformed by acceleration, an acceleration compensator is also provided.
These sensors cannot measure static pressures for more than a couple seconds, but are capable of measuring dynamic phenomena such as shock; vibration; pressures associated with blasts, explosions, or pulsation; or the dynamic conditions in rocket motors, engines, compressors, and etc.
Because of the dynamic nature of this sensor, its output is usually expressed in relative pressure units (such as PSIR), where the measurement is referenced to the initial conditions that existed prior to the transient event or to the average of a cycling pressure. Natural or cultured quartz and natural tourmaline are both used as sensors in piezoelectric transducers. Quartz is inexpensive, stable, and insensitive to temperature changes.
The main advantages of piezoelectric pressure sensors include their small size, rugged construction, high speed of response, and self-generated signal. These sensors are limited to dynamic measurements, are sensitive to temperature variations, and require special cabling and output signal amplification.
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