An accelerometer including: a housing having an internal cavity; a piezoelectric material disposed in the internal cavity; a mass movable disposed in the internal cavity; and a spring disposed between the piezoelectric material and a portion of the housing, the spring being compressively preloaded against the piezoelectric material; wherein the mass is movable when the housing experiences an acceleration such that the mass acts upon the spring and the spring acts against the piezoelectric material, the piezoelectric material outputting a signal corresponding to a magnitude of the acceleration.

Voice control is extended outside of an automotive vehicle by an access system associated with a door and window. An accelerometer is mounted on the window to generate a vibration signal. A passive entry system generates an unlock standby signal when an authorized user carrying a wireless fob is detected proximate the door. A voice recognizer in the vehicle is activated by the standby signal to scan the vibration signal for a spoken command for opening the door. A door actuator is activated by the voice recognizer when the command is detected.

An acceleration transducer defines a rectangular coordinate system with two orthogonal horizontal axes that are both normal to a vertical axis and includes a main body defining tangential side faces arranged tangentially to the vertical axis, and normal side faces arranged normally to the vertical axis. The transducer includes at least a first piezoelectric element secured to one the three tangential side faces, and exactly one seismic mass is secured to the at least one piezoelectric element, which has a high sensitivity for a shear force exerted by the attached seismic mass along a principal tangential axis and a low sensitivity for a shear force exerted by the attached seismic mass along another one of the three axes.

A sensor includes two shear-mode piezoelectric transducers, wherein each piezoelectric transducer has a bottom surface and a top surface, wherein the top surfaces of the piezoelectric transducers are rigidly connected to each other, and wherein the bottom surfaces of the piezoelectric transducers are configured to be attached to an object to be measured.

A shear-type piezoelectric sensor and a method for manufacturing the shear-type piezoelectric sensor are provided. The shear-type piezoelectric sensor comprises a collar, a piezoelectric element, and a mass block, wherein the collar is disposed outside a fastening nail, the fastening nail can be screwed onto a support arranged on a base; the piezoelectric element is disposed outside the collar; the mass block is disposed outside the piezoelectric element, the collar is expanded as the fastening nail is screwed onto the support, the piezoelectric element is expanded by an expanding force transferred from the collar, and the mass block is expanded by an expanding force transferred from the piezoelectric element. The shear-type piezoelectric sensor can be assembled easily and has high sensitivity and can be used in a high-temperature environment.

An acceleration transducer defines a rectangular coordinate system with two orthogonal horizontal axes that are both normal to a vertical axis and includes a main body disposed within a housing and defining tangential side faces arranged tangentially to the vertical axis, and a normal side face arranged normally to the vertical axis. A piezoelectric element is secured to one of the tangential side faces, and a seismic mass is secured to the piezoelectric element. A signal output is attached to the housing and includes a signal conductor spaced apart by an assembly gap from a tangential side face that is not attached to the piezoelectric element. The assembly gap extends perpendicularly to the vertical axis. The normal side face includes at least one main body output conductor spanning the assembly gap in a direction perpendicular to the vertical axis and directly contacting the signal conductor.

A shear mode piezoelectric accelerometer includes a ring-shaped piezoelectric element, a central shaft, a mass block, a first electrode, and a second electrode. The ring-shaped piezoelectric element includes an outer ring wall and an inner ring wall. The central shaft is made of conductive material and is fixed through the inner ring wall of the ring-shaped piezoelectric element. The mass block is made of conductive material and includes a fixed element and a weight element. The fixed element has a fixed hole and is fixed to the outer ring wall of the ring-shaped piezoelectric element by fitting the fixed hole. The weight element is located on the fixed element on the opposite side away from the fixed hole. The first electrode is electrically connected to the central shaft. The second electrode is electrically connected to the mass block.

Wireless piezoelectric accelerometers and systems are provided. A wireless piezoelectric accelerometer may comprise a piezoelectric sensing element configured to sense mechanical acceleration and produce an electrical charge signal in response of the sensed mechanical acceleration, a signal processing module (SPM) configured to convert the electrical charge signal into a voltage signal, and process and digitize the voltage signal, and a wireless module configured to modulate and transmit the digitized voltage signal as wireless signals. The piezoelectric sensing element, the SPM and the wireless module are packaged in a casing. The casing comprises a metallic shielding chamber configured to enclose the piezoelectric sensing element. The casing further comprises a non-metallic portion located in relative to the wireless module to allow transmission of the wireless signals. Corresponding wireless piezoelectric accelerometer systems are also provided.

An on-site reciprocity calibration method for a piezoelectric accelerometer, including a vibration test and a reciprocity test. In the vibration test, a sine excitation with a corresponding frequency and amplitude is provided by a vibration exciting device to the piezoelectric accelerometer fixed on a motion plane, and output signals of a drive port and a signal port of the reciprocal piezoelectric accelerometer are collected by a data acquisition device. In the reciprocity test, a sine voltage excitation is provided by a signal generator to the drive port, and then an excitation signal and an output signal of the signal port are collected by the data acquisition device. An amplitude ratio of the two signals is obtained based on signal sine-fitting. Finally, the on-site calibration is enabled according the sensitivity amplitude ratio obtained in the vibration test and the sensitivity amplitude product obtained in the reciprocity test.

A surface mountable piezoelectric sensor includes a pair of oppositely polarized, spaced, parallel piezoelectric members separated by an isolator. A first electrode is associated with the piezoelectric members bridging the isolator resulting in a series circuit when the pair of piezoelectric members are mounted to a printed circuit board. A second electrode is associated with one piezoelectric member and electrically isolated from a third electrode associated with the other piezoelectric member for surface mounting to the printed circuit board.