A piezoelectric system can be constructed for virtually any application for which any other type of electromechanical transducer can be used. For any particular application, however, limiting factors include the size, weight, and cost of the piezoelectric system. Piezoceramic ceramic devices fit into four general categories: piezo generators, sensors, piezo actuators, and transducers. Characteristics of each group are briefly summarized here.
Alternatively, the electrical energy generated by a piezoelectric element can be stored. Techniques used to make multilayer capacitors have been used to construct multilayer piezoelectric generators. Such piezo generators are excellent solid state batteries for electronic circuits.
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Piezoelectric SensorsA piezoelectric sensor converts a physical parameter, such as acceleration or pressure, into an electrical signal. In some sensors the physical parameter acts directly on the piezoelectric element; in other devices an acoustical signal establishes vibrations in the element and the vibrations are, in turn, converted into an electrical signal. Often, the system provides a visual, audible, or physical response to the input from the piezo sensor -- automobile seatbelts lock in response to a rapid deceleration, for example.
Piezo Actuators: Multilayer, Stack, Bending, StripeA piezo actuator converts an electrical signal into a precisely controlled physical displacement, to finely adjust precision machining tools, lenses, or mirrors. Piezoelectric actuators also are used to control hydraulic valves, act as small-volume pumps or special-purpose motors, and in other applications. Piezoelectric motors are unaffected by energy efficiency losses that limit the miniaturization of electromagnetic motors, and have been constructed to sizes of less than 1 cm3. A potentially important additional advantage to piezoelectric motors is the absence of electromagnetic noise.
There are two different types of piezo actuators / piezo multilayers. The first is a stack actuator. A stack actuator is constructed in one of two ways: discrete stacking or co-firing depending on the user’s requirements.
The other type of piezo actuator is a stripe actuator or bending actuator, in which thin layers of piezoelectric ceramics are bonded together; the thin layers allow the actuator to bend with a greater deflection but a lower blocking force than a stack actuator.
Alternatively, if physical displacement is prevented, a piezo actuator will develop a usable force.
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Piezoelectric transducers convert electrical energy into vibrational mechanical energy, often sound or ultrasound, that is used to perform a task.
Piezoelectric transducers that generate audible sounds afford significant advantages, relative to alternative electromagnetic devices -- they are compact, simple, and highly reliable, and minimal energy can produce a high level of sound. These characteristics are ideally matched to the needs of battery-powered equipment.
Because the piezoelectric effect is reversible, a transducer can both generate an ultrasound signal from electrical energy and convert incoming sound into an electrical signal. Some devices designed for measuring distances, flow rates, or fluid levels incorporate a single piezoelectric transducer in the signal sending and receiving roles, other designs incorporate two transducers and separate these roles.
Piezoelectric transducers also are used to generate ultrasonic vibrations for cleaning, atomizing liquids, drilling or milling ceramics or other difficult materials, welding plastics, medical diagnostics, or for other purposes.
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