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Low Voltage and High Voltage PZTs
Two main types of piezo actuators are available: low voltage (multilayer) devices requiring about 100 volts for full motion and high voltage devices requiring about 1000 volts for full extension. Modern piezo ceramics capable of greater motion replace the natural material used by the Curies, in both types of devices. Lead zirconate titanate (Piezo) based ceramic materials are most often used today. Actuators made of this ceramic are often referred to as Piezo actuators.
The maximum electrical field Piezo ceramics can withstand is on the order of 1 to 2 kV/mm. In order to keep the operating voltage within practical limits, Piezo actuators consist of thin layers of electroactive ceramic material electrically connected in parallel. The net positive displacement is the sum of the strain of the individual layers. The thickness of the individual layer determines the maximum operating voltage for the actuator (for more information click here).
High voltage piezo actuators are constructed from 0.5 to 1.0 mm layers while low voltage piezo actuators are monolithic (diffusion bonded) multilayer designs constructed from 20 to 100 µm layers.
Both types of piezo actuators can be used for many applications: Low voltage actuators facilitate drive electronics design, high voltage types operate to higher temperatures (150 °C compared to 80 °C). Due to manufacturing technology high voltage ceramics can be designed with larger cross-sections for higher load applications (up to several tons) than low voltage ceramics.
Electrical connection of disks in a Piezo stack actuator.
Resolution
Piezo actuators have no "stick slip" effect and therefore offer theoretically unlimited resolution. This feature is important since PZTs used in atomic force microscopes are often required to move distances less than one atomic diameter. In practice, actual resolution can be limited by a number of factors such as piezo amplifier (electric noise results in unwanted displacement), sensor & control electronics (noise and sensitivity to EMI affect the positional resolution and stability) and mechanical parameters (design and mounting precision of the sensor, actuator and preload influence micro-friction which limits resolution and accuracy). PI Closed Loop Piezo Actuators provide sub-nanometer resolution and stability.
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>> Piezoelectric Actuators
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Electrical connection of disks in a Piezo stack actuator.
Resolution
Piezo actuators have no "stick slip" effect and therefore offer theoretically unlimited resolution. This feature is important since PZTs used in atomic force microscopes are often required to move distances less than one atomic diameter. In practice, actual resolution can be limited by a number of factors such as piezo amplifier (electric noise results in unwanted displacement), sensor & control electronics (noise and sensitivity to EMI affect the positional resolution and stability) and mechanical parameters (design and mounting precision of the sensor, actuator and preload influence micro-friction which limits resolution and accuracy). PI Closed Loop Piezo Actuators provide sub-nanometer resolution and stability.