An impedance measurement system for piezoelectric array element transducers

Abstract

Abstract Impedance measurement of piezoelectric element materials is an important factor to estimate the transducer performances. The measurement method involves manually contacting the surface of the piezoelectric material. However, this method is not appropriate to measure the impedance accurately, since the element size of the ultrasound transducers used for the cardiovascular, trans-esophageal, and transrectal areas is small. Therefore, reliability issues are a critical concern of the miss-contact generated by human errors or inaccuracy of the contact positions produced by non-constant pressures. In order to resolve the issue, we developed a novel impedance measurement system (IMS) for piezoelectric array element transducers through precise motion control techniques. The basic structure of the system uses a 3-axis motion stage. The control program is to drive the motion control and data acquisition units with the impedance analyzer. Each axis of the motion control stages has a 10 μm resolution, which can measure fine-pitch of the array elements that has less than 0.5 mm. The control program can provide the functions to define the velocity of the each motion and moving distances per one pulse. The electrical impedances (EIs) were measured using a precise 50 Ω resistor around 10 times in order to prove the reliability of the IMS. The results showed that the value of the minimum and maximum measured EI values were 50.83 Ω and 50.95 Ω, respectively. The maximum standard deviation of the each element was 7.6253 × 10−3 Ω, indicating that the standard deviation was under 8 × 10−3 Ω. Therefore, the IMS provides accurate capability of the repeatable impedance measurement. The EIs of the randomly selected transducer elements were also measured by this system. This system could be useful to repair, manufacture and research of the ultrasound array element transducers.