Exact rates of aging depend on the composition of the ceramic element and the manufacturing process used to prepare it. Stability- Most properties of a piezoelectric ceramic element erode gradually, in a logarithmic relationship with time after polarization. Dielectric losses usually are more significant than mechanical losses. Dielectric losses and mechanical losses also affect the efficiency of energy conversion. k depends on the mode of vibration and the shape of the ceramic element. The values for minimum impedance frequency and maximum impedance frequency can be used to calculate the electromechanical coupling factor, k, an indicator of the effectiveness with which a piezoelectric material converts electrical energy into mechanical energy or mechanical energy into electrical energy. These frequencies are determined by experiment - to see how, refer to Determining Resonance Frequency. As the frequency is further increased, impedance increases to a maximum (minimum admittance), which also is the anti-resonance frequency. This frequency also is the resonance frequency.
The frequency at which the element vibrates most readily in response to the electrical input, and most efficiently converts the electrical energy input into mechanical energy - the resonance frequency - is determined by the composition of the ceramic material and by the shape and volume of the element.Īs the frequency of cycling is increased, the element's oscillations first approach a frequency at which impedance is minimum (maximum admittance). S: strain (change in height / original height of element)Ī piezoelectric ceramic element exposed to an alternating electric field changes dimensions cyclically, at the frequency of the field. Δh: change in height (thickness) of ceramic element Where l: initial length of ceramic element The relationships between an applied voltage or electric field and the corresponding increase or decrease in a piezoelectric ceramic element's thickness, length, or width are:
Behavior of a Piezo Element Influence of Input FrequencyĪt low input frequencies, the relationships between a force applied to a piezoelectric ceramic element and the electric field or charge produced by the piezo element are:
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