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We are also able to analyze the specifications what happens signal conditioning by using charge amplifier. A signal-conditioning circuit must have low imput impedance but piezoelectric transcuder have high input impedance which is bad thing. A typical input impedance for piezoelectric transducer is 3500 kΩ but it varies in different piezoelectric models.
Sources
http://www.engineersgarage.com/articles/pressure-sensors-types-working
http://www.sensorsmag.com/sensors/pressure/fundamentals-pressure-sensor-technology-846
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