Abstract: A device includes a piezoelectric transducer. The transducer has N independent transducer regions. N is an integer. Each of the N independent transducer regions has a thickness. Each of the N independent transducer regions has an acoustic impedance AIT. Each of the N independent transducer regions is independently excitable to oscillate in the thickness mode when electrically excited by a potential difference applied across the thickness. The device further includes a first impedance matching layer having an acoustic impedance AI1 and AIT and a borehole fluid acoustic impedance AIBF. The first impedance matching layer is situated such that an acoustic signal emitted by the piezoelectric transducer will pass through the second impedance matching layer. The device further includes a second impedance matching layer having an acoustic impedance AI2 between AI1 and AIBF.

Abstract: Technologies are described for reducing distortion in amplified signals in well logging tools based on spectral analyses of the amplified signals. For example, a system includes a well logging tool. The well logging tool includes an excitation source to direct an excitation signal towards an environment adjacent a wellbore and a receiver to amplify a probe signal received from the environment adjacent the wellbore in response to the excitation signal. The system also includes a feedback module to receive the amplified signal. The feedback module includes a spectrum analyzer module to spectrally analyze the amplified signal to generate spectral information of the amplified signal; and a controller module to determine, from the spectral information, whether the amplified signal includes distortion, and if so, to issue a feedback signal to the excitation source or the receiver to cause at least a reduction of the distortion in the amplified signal.

Abstract: An example variable reluctance device includes a load structure connected to an armature through a connecting arm. The armature is positioned between two oppositely oriented core structures. A structural frame secures the core structures in a fixed position, forming gap regions between the core structures and the armature, forming a magnetic circuit. The armature is resiliently centered between the core structures by a spring, such that the gaps and are approximately equal in width when the armature is at rest. The device further includes a magnetic substance within the gaps that is compressed or stretched to allow movement of the armature.

Abstract: An ultrasonic transducer device is disclosed. The device includes a body and an ultrasonic transducer mounted onto the body. The ultrasonic transducer comprises a shoulder and an O-ring placed on the shoulder. The O-ring substantially covers the interface between the ultrasonic transducer and the body.

Abstract: A device includes a piezoelectric transducer. The transducer has N independent transducer regions. N is an integer. Each of the N independent transducer regions has a thickness. Each of the N independent transducer regions has an acoustic impedance AIT. Each of the N independent transducer regions is independently excitable to oscillate in the thickness mode when electrically excited by a potential difference applied across the thickness. The device further includes a first impedance matching layer having an acoustic impedance AI1 and AIT and a borehole fluid acoustic impedance AIBF. The first impedance matching layer is situated such that an acoustic signal emitted by the piezoelectric transducer will pass through the second impedance matching layer. The device further includes a second impedance matching layer having an acoustic impedance AI2 between AI1 and AIBF.

Abstract: A focused acoustic transducer suitable for use in a downhole environment is disclosed. At least some embodiments employ a disk of piezoelectric material with low planar coupling and low Poisson's ratio mounted on a backing material and sealed inside an enclosure. The piezoelectric material disk has a pattern of electrodes deposited on an otherwise smooth, ungrooved surface. Despite the lack of grooves, the material's low planar coupling and low Poisson's ratio enables the electrodes to operate in a phased relationship to provide and receive focused acoustic pulses. Moreover, the elimination of deep cuts offers a much lower cost of construction. The electrode material may be any conductive material, though silver and silver alloys are contemplated. The patterning of electrodes can occur during the deposition process (e.g., using a silk-screen or other printing technique) or afterwards (e.g., mechanically or chemically with an etch technique that uses a pre- or post-deposition photoresist layer).