Piezoelectric elements

What are piezoelectric elements?

Piezoelectric elements are used in a wide range of applications, including buzzers, sensors, and filters. Since resonant and antiresonant frequencies characterize their impedance/frequency characteristics, an impedance analyzer is the ideal instrument for use in analyzing their characteristics. 

Setting example of measurement conditions

Measurement modesANALYZER
Sweep parameterFREQ
Sweep frequencySet to a range within which the resonant, anti-resonant frequency can be checked.
Signal levelDepends on the measurement items
Equivalent circuit modelE
*The above settings apply to an example measurement. Since optimal conditions vary with the measurement target, specific settings should be determined by the instrument operator.

Equivalent circuit of piezoelectric elements

Close to its resonant frequency, a piezoelectric element can be depicted as an electrical equivalent circuit. Specifically, such an element can be depicted as a parallel capacitance CO that is connected in parallel to a series circuit consisting of the series inductance L1, the series capacitance C1, and the series resistance R1. 

Actual measurement and analysis

The image describes actual measurement and analysis with an IM3570 and IM9000 (optional equivalent circuit analysis software).

Recommended products

IM3590DC,1mHz to 200kHzAnalyzer mode (low frequency), equivalent circuit analysis
DC,4Hz to 5MHzFrequency sweep with analyzer mode
IM7581100kHz to 300MHzAnalyzer mode (high frequency), equivalent circuit analysis
*For more information, please see the product catalog.

Measuring resonant frequency and anti-resonant frequency

The frequency fm characterized by minimum inductance and the frequency fn characterized by maximum inductance can be calculated from the element’s impedance/frequency characteristics using the instrument’s peak search function. In addition, it is possible to calculate the resonant frequency fr, which is characterized by a phase of 0, and the antiresonant frequency fa.

The series resonant frequency fs and the parallel resonant frequency fp can be expressed as shown on the right.

Equivalent circuit analysis

Pass/fail judgments using analyzer mode

Either of two methods can be used to generate pass/fail judgments when using analyzer mode: peak judgment and area judgment.

Judgement areas can be set as follows.   
• A known-good element’s measured value can be used as the reference (±10% of the reference element’s measured value, etc.).
• A user-specified value can be entered (1 k±10%, etc.).