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Environmental Considerations
Application of PZTs in Normal AtmosphereThe insulation materials used in standard piezo actuators are sensitive to humidity. These PZTs are not recommended in environments with high relative humidity (more than 75%). For higher humidity environments PI offers special systems with hermetically sealed stacks, or integrated dry air flushing mechanisms.
Application of PZTs in Inert Gas Atmosphere
Piezo actuators can be damaged if operated at maximum drive voltage in a helium or argon atmosphere. Low Voltage actuators are recommended for these conditions. To reduce the risk of dielectric breakdown, the PZTs should be operated at minimum possible voltage (HVPZTs: ‹ 300 V, LVPZTs: ‹ 80 V). Semibipolar operation helps to further reduce the electrical field strength while yielding reasonable displacement.
Vacuum Application of PZTs
When piezo actuators are used in a vacuum, two factors must be considered:
1) dielectric stability
2) outgassing
The dielectric strength of a gas is a function of pressure. Air displays a high insulation capability at atmospheric pressure and below 10-2 Torr. However, in the range from 10 to 0.01 Torr (corona area) insulation properties are degraded. PZTs should not be operated in this range because an electric breakdown may occur.
All PI piezo actuators can be operated at pressures below 0.01 Torr. Outgassing (of the insulation materials) may limit their use in applications where contamination or virtual leaks are an issue. Outgassing behavior varies from model to model depending on construction. High vacuum options for minimum outgassing are available for several standard LVPZTs and HVPZTs (see "Piezo Actuators" section for details). UHV compatible Piezo Flexure Positioners are available on request.
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