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Piezoelectric pressure transducers

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Field Instrumentation

Response time The time required for an output to make the change from an initial value to a large specified percentage, usually 90, 95 or 99% of the final value.

Piezoelectric pressure transducers
A material that produces electric voltage when pressure is applied is referred to as piezoelectric material, like barium titanate powder and crystals of quartz, tourmaline, and Rochelle salts.
• Piezoelectric pressure transducers are force balance transducers.
• To amplify the voltage signal, amplifier input impedance should be high (greater than 100 M ohms.
• It can measure up to 50000 psi. The instrument can indicate a pressure increase over the full range in a period of time as short as 1 microseconds Piezoelectric transducers cannot measure steady pressures. They respond only to changing pressures. Pressure at Pis transmitted to the piezoelectric crystal, Y, by a diaphragm. The signal is amplified by a charge amplifier. A second piezoelectric crystal, Y, is included to compensate for any acceleration of the device during use. Signals from the compensating crystal are amplified by a second charge amplifier. A

46 Field Instrumentation GEN Rev) difference amplifier subtracts the amplified compensating signal from the amplified signal produced by the pressure crystal. The difference indicates the resulting pressure. Piezoelectric pressure transducers
Response time

The time required for an output to make the change from an initial value to a large specified percentage, usually 90, 95 or 99% of the final value.

2.5 Environmental conditions
affecting a transducer
Ambient temperature: temperature of air surrounding a device.
Relative humidity: a measure of the moisture content of the air, specified as a range of percent RH at a reference temperature. Temperature and relative humidity combine to produce condensation.
Vibration: Oscillation or motion of device about its position of rest.

47 Field Instrumentation GEN Rev)

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