Zhejiang University

National Institute of Metrology P.r. China

Shushi Jia

Jie Zhou

Wen He

Chunyu Wang

Runjie Shen

Mei Yu

Mingde Ma

Longbiao He

Yuanlai Zhou

Guanhua Xu

Jinlin Li

The infrasound generating device based on a displacement-feedback type vibration exciter comprises a displacement-feedback type vibration exciter system, an infrasound generating chamber () and a laser vibrometer (); the displacement feedback mechanism is adopted in the vibration exciter (). The piston () is driven by the vibration exciter to move in a sinusoidal manner in the cavity () of the airtight infrasound generating chamber () and the standard infrasonic pressure signal with low harmonic distortion can be achieved. The displacement of the moving part () of the vibration exciter () can be measured by the laser vibrometer () through the measurement beam () injecting into the vibration exciter () through the optical channel running through the vibration exciter and the standard infrasonic pressure can also be obtained. The value of the standard sound pressure produced by the infrasound generating chamber is calculated. Such value is used as the calibration reference for the infrasound sensors () to be calibrated in order to achieve the primary calibration of the infrasound sensors. The standard infrasonic sensor can be installed inside the infrasound generating chamber () and the output of the standard infrasonic sensor can be used as the reference for the infrasonic sensor () to be calibrated in order to achieve the secondary calibration of the infrasound sensors. This invention has the advantages of technical maturity, high feasibility, easy to realize, high calibration accuracy and so on.

Infrasound generating device based on a displacement-feedback type vibration exciter

The electromagnetic vibration exciter system with an adjustable electro-viscoelastic suspension device comprises an electromagnetic vibration exciter, a power amplifier and an adjustable electro-viscoelastic suspension device, which acts as the suspension device of the electromagnetic vibration exciter. The adjustable electro-viscoelastic suspension device contains a displacement sensor detecting the displacement of the moving component, a first adjustable amplifier and a second adjustable amplifier, a differentiator, an adjustable phase shifter, an adder and a proportioner. The linearity of the stiffness and damping of the exciter system is excellent, which can be adjusted as need through the adjustment of gain of the adjustable amplifier, the proportioner, the adjustable phase shifter. This invention has adjustable and linear parameters and it is also easy to be realized.

Electromagnetic vibration exciter system with adjustable electro-viscoelastic suspension device

The vibration exciter system with a feedback control unit based on an optical linear encoder includes a vibration exciter, a signal generator and a power amplifier. The exciter system further comprises an optical linear encoder converting the displacement of moving component of the exciter into A/B pulse with a phase difference of 90&#xb0; , a filtering, shaping and level translator unit converting the A/B pulse into standard pulse with standard shape and level, a subdivider and orientation recognizer unit refining standard pulse and recognizing the moving orientation, an analog converter unit converting refined standard pulse into analogue signal that reflects the displacement of the moving component. The standard signal outputted by the signal generator and the converted analogue signal are inputted into a subtracter as the minuend and subtrahend respectively. The output of the subtracter is inputted into the power amplifier and then into the vibration exciter as a driving signal.

Vibration exciter system with a feedback control unit based on an optical linear encoder

A precision tilting platform used for static calibration of seismometers includes a base, a worktable, a rotary part, a driving part, a measuring part and supporting frames. The rotary part includes a shaft, a driving arm, a rotary table and a clump weight. The driving part includes a linear motor, a sliding table, a pair of linear guides and sliders and a grating scale. The readhead of the grating scale is fixed with the base and sends out a signal of zero position when the worktable is horizontal. The sliding table contacts the driving arm. When the linear motor is moving forward, the rotary part rotates toward the positive direction. When the linear motor is moving backward, the rotary part rotates toward the negative direction under gravity of the clump weight. The measuring part includes a laser interferometer and a reflector to obtain the tilting angle of the worktable.

Precision tilting platform device used for static calibration of seismometers

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Hangzhou, China

Shushi Jia