Venting in the Comparative Study of Flexural Ultrasonic Transducers to Improve Resilience at Elevated Environmental Pressure Levels

Andrew Feeney,Lei Kang,Steve Dixon,William E Somerset

doi:10.1109/jsen.2020.2974547

Abstract

The classical form of a flexural ultrasonic transducer is a piezoelectric ceramic disc bonded to a circular metallic membrane. This ceramic induces vibration modes of the membrane for the generation and detection of ultrasound. The transducer has been popular for proximity sensing and metrology, particularly for industrial applications at ambient pressures around 1 bar. The classical flexural ultrasonic transducer is not designed for operation at elevated pressures, such as those associated with natural gas transportation or petrochemical processes. It is reliant on a rear seal which forms an internal air cavity, making the transducer susceptible to deformation through pressure imbalance. The application potential of the classical transducer is therefore severely limited. In this study, a venting strategy which balances the pressure between the internal transducer structure and the external environment is studied through experimental methods including electrical impedance analysis and pitch-catch ultrasound measurement. The vented transducer is compared with a commercial equivalent in air towards 90 bar. Venting is shown to be viable for a new generation of low cost and robust industrial ultrasonic transducers, suitable for operation at high environmental pressure levels.

Highlights

T HE measurement of ultrasound is essential for a range of applications in different industries, for example proximity sensing for robotics or automobiles, and flow measurement in the petrochemical, water, and energy industries
The flexural ultrasonic transducer is commonly used for the generation or detection of ultrasound in automotive parking sensor applications, or in metrological systems such as flow measurement [1]–[3]
We demonstrated fundamental ultrasound measurement principles for transducers operating in environments with elevated pressure levels and the reliability potential of the vented configuration

Summary

Introduction

T HE measurement of ultrasound is essential for a range of applications in different industries, for example proximity sensing for robotics or automobiles, and flow measurement in the petrochemical, water, and energy industries. Developments in ultrasonic transducer technology are required to meet the demands of industry, and in particular the measurement of ultrasound in hostile environments, such as those of high pressure. The flexural ultrasonic transducer is commonly used for the generation or detection of ultrasound in automotive parking sensor applications, or in metrological systems such as flow measurement [1]–[3]. The classical flexural ultrasonic transducer (CFUT) typically comprises a cap housing, containing a Manuscript received January 21, 2020; revised February 14, 2020; accepted February 14, 2020. Date of publication February 21, 2020; date of current version May 5, 2020. The associate editor coordinating the review of this article and approving it for publication was Dr Qiang Wu.

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