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Overview of Vibration Measurement Related Equipment

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.

Structure and Principle of Acceleration Detectors

Structure and Principle of Acceleration Detectors

Single crystal quartz and titanium barium generate charges on their surface 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 type acceleration pickup is a sensor that uses the piezoelectric element as a spring in a size mode system, while also functioning as a mechanical-electrical conversion element. It outputs an electrical signal proportional to the vibrational acceleration.

The piezoelectric type acceleration pickup is fundamentally 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 where the piezoelectric element is sandwiched between the sensor base and the weight.
In contrast, the shear type has a structure where the piezoelectric element is fixed between a post standing vertically on the base and the weight.

Traditionally, the compression type was used, but recently, the shear type, which is less affected by base strain and sudden temperature changes, has become more common. Our piezoelectric type acceleration detectors are mostly shear type, with some exceptions.

For more details, please read our technical report "About Vibration and Its Sensors."

　
Vibration and its sensors

Acceleration detector (acceleration pickup) - vibration detection - related products

Vibration Analysis and Diagnosis Related Products

recording

Analysis

Judgement

The principle of the Laser Doppler Vibrometer

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.

  • The principle of the Laser Doppler Vibrometer

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'.

Laser Doppler Vibrometer

Laser interferometric displacement meter / Laser length measuring device / Laser in-plane velocity meter

  • The described items may be subject to change.

  • The displayed price is listed as a reference for domestic prices in Japan.

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