振動計測 関連機器 概要

Ono Sokki offers a wide range of measurement instruments, including accelerometers, impulse hammers used for natural frequency measurement and modal analysis, and Laser Doppler Vibrometers for high-sensitivity vibration measurement, as well as analysis equipment for the acquired vibration data. We provide a total system for vibration measurement and analysis that combines all of these for various applications. Additionally, we also offer consulting services for the acquisition and analysis of vibration data.

Single crystals of quartz and titanium barium generate electric charge on their surfaces when subjected to force. This phenomenon is called the piezoelectric effect. Materials that exhibit the piezoelectric effect are referred to as piezoelectric materials (piezoelectric elements).

The piezoelectric accelerometer is a sensor that uses a piezoelectric element as a spring in a mechanical system and simultaneously as a mechanical-electrical conversion element. It outputs an electrical signal proportional to the vibrational acceleration.

Piezoelectric accelerometers are broadly classified into two types: compression type and shear type, based on the way force is applied to the piezoelectric element. Structural diagrams of each type are shown.

The compression type has a structure that sandwiches a piezoelectric element between the base of the sensor and the weight.
The share type has a structure that fixes a piezoelectric element between a post erected vertically on the base and the weight.

Traditionally, compression-type accelerometers were used; however, recently, share-type accelerometers have become popular due to their reduced sensitivity to base distortion and rapid temperature changes. Our piezoelectric accelerometers are mostly share-type, with some exceptions.

For more details, please read this technical report 'About Vibrations and Their Sensors'.

When sound waves, radio waves, or light waves with a certain frequency component are directed at an object moving at a certain speed, the frequency changes in proportion to the speed component of the moving object. This is called the Doppler shift or Doppler effect.

At this time, the following relationship holds between the emitted frequency and the frequency that has been reflected back.

If an object is approaching 　emission frequency < reflection frequency
If an object is moving away 　　　emission frequency > reflection frequency

The difference between the emission frequency and the reflection frequency is related to the speed of the object, and generally, as the speed increases, the difference in frequency becomes larger. The Laser Doppler Vibrometer uses this principle. When laser light is irradiated onto a moving target, the frequency of the reflected light from the target is Doppler shifted from the frequency that the irradiated light originally possesses due to the Doppler effect.
Looking at the amount of Doppler shift at this time, let the shifted frequency be fD, the speed of the target be V, the wavelength of the irradiated light be λ, and the angle between the direction of the irradiated light and the direction of the target's movement be θ, then the following equation holds.

Here, if we denote the frequency of the laser irradiation light as f0, the frequency of the reflected light will be f0 + fD.
Since the wavelength λ of the laser light used in the Laser Doppler Vibrometer is extremely stable, the Doppler frequency fD and the target's velocity V are in a proportional relationship.
Additionally, in the Laser Doppler Vibrometer, the angle θ between the direction of the laser irradiation and the direction of the target's movement is usually set to 0 degrees (detecting only the parallel component of the reflected light to the incident light: out-of-plane vibration*), allowing us to determine the velocity of the target in the direction of irradiation by measuring the Doppler frequency fD.
However, since the frequency of the laser light itself is extremely high and difficult to measure directly, the detection of the Doppler frequency fD is usually done by
interfering the irradiation light (f0) and the reflected light (f0+fD).

For more details, please read this technical report 'About Vibrations and Their Sensors'.

If you are considering a purchase, please check with the nearest our sales office or agent.