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Piezoelectric sensors measure pressure or strain by converting force into an electrical signal. They can be made from natural or synthetic materials and are used in various applications, including measuring impact forces and detecting unusual vibration patterns. They are also used in microphones, touch screens, and scientific research.
A piezoelectric sensor is a device that measures pressure or strain using piezoelectricity, a phenomenon whereby certain materials can generate an electric current when deformed. So a piezoelectric sensor can convert the force exerted on it by compression, impact, acceleration or vibration into an electrical signal whose strength is proportional to the strength of the force. There are a number of natural materials that demonstrate this effect, most notably quartz and tourmaline. Piezoelectric materials can also be synthesized industrially. Synthetic piezoelectric materials can be single crystal materials similar to natural crystals but with improved properties, such as gallium phosphate crystals; piezoceramic materials such as lead zirconate titanate (PZT), which can be produced at low cost by sintering or heating powdered ingredients in a furnace; and polymers such as polyvinylidene fluoride (PVDF) which can be made into flexible thin films.
The electrical signal generated by piezoelectric sensors decreases rapidly after the first application of force. This means they are not suitable for measuring a static force; however, they are excellent for measuring forces of very short duration, such as impact forces. Single crystal and piezoceramic sensors are very stiff and have a very high natural frequency. The natural frequency of a sensor imposes limitations on its use, as measurement errors will occur when the frequency of the vibration to be measured is close to that of the sensor. However, the high natural frequency of a piezoelectric sensor allows very high frequencies to be measured accurately. This means it can be used to detect unusual vibration patterns that could be caused by material and component defects.
The high rigidity of single crystal and piezoceramic sensors means that they often have similar physical properties to the materials, such as steel, from which tools and machines are made. The sensors can then be incorporated into tools and machinery as part of their structure, so they can be built with integrated sensors. This type of piezoelectric sensor is also very robust, being able to handle high impact forces and operate effectively at high temperatures, and is used in many industrial applications to measure pressure and strain on materials. They can also be used to measure acceleration: when an object accelerates, it exerts a force in the opposite direction which can be measured by a sensor.
Piezoelectric sensors have a wide range of other applications. A common application is in microphones, where the force exerted by sound waves is converted into electrical signals and recorded or amplified. Flexible and lightweight piezoelectric materials such as PVDF can be used in touch screens and touch pads, and also have applications in scientific research. For example, tiny sensors can be attached to small animals and even insects to monitor their activity and behavior.
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