Vibration is one of the most common phenomena in nature, existing everywhere from the universe to atomic particles. Vibration is ubiquitous in engineering and technology, but in many cases it is harmful. For example, vibration reduces machining accuracy and surface finish, exacerbates fatigue and wear of structural components, and in the automotive and aerospace industries, vibration of the fuselage and structural components not only affects driver operation and comfort but can also, in severe cases, cause fractures or even disintegration of the fuselage and structural components.
Vibration sensors are used to detect impact force or acceleration. They typically use piezoelectric devices that generate an electric charge when stress is applied, but there are also sensors that can detect vibration using other materials and methods.
Vibration sensors can be used for long-term monitoring of vibration and displacement in machinery, thermal expansion of rotors and housings; online automatic detection and control of production lines; and measurement of various minute distances and movements in scientific research. Vibration sensors are widely used in energy, chemical, medical, automotive, metallurgical, machinery manufacturing, military, scientific research and teaching, and many other fields.
There are many ways to measure vibration using vibration sensors, but in summary, most of them use the following three principles:
Mechanical measurement method: The change in engineering vibration is converted into a mechanical signal, which is then amplified by a mechanical system before measurement and recording. Commonly used instruments include lever-type vibration meters and Geiger vibration meters. This method has a relatively low measurement frequency and poor accuracy, but it is very convenient to operate.
Optical measurement methods: These methods convert changes in engineering vibration into optical signals, which are then amplified by an optical system for display and recording. Laser vibration meters, for example, employ this method.
Electrical measurement method: This method converts changes in engineering vibration into electrical signals, which are then amplified, displayed, and recorded. It first converts mechanical vibration into electrical quantities, then measures them, and determines the magnitude of the vibration based on the corresponding relationships. This is currently the most widely used vibration measurement method.
As can be seen from the three measurement methods above, they all involve three steps: vibration sensor, signal amplification circuit, and display and recording.
Classification of vibration sensors
In terms of mechanical receiving principles, vibration sensors are only of two types: relative and inertial. However, in terms of electromechanical transformation, due to differences in transformation methods and properties, there are many types of vibration sensors with extremely wide applications. The sensors used in modern vibration measurement are no longer independent mechanical measuring devices in the traditional sense; they are only one component of the entire measurement system and are closely related to subsequent electronic circuitry.
Due to the different electromechanical conversion principles within the sensors, the output electrical quantities also vary. Some sensors convert changes in mechanical quantities into changes in electromotive force or electric charge, while others convert changes in mechanical vibration into changes in parameters such as resistance and inductance.
Generally speaking, these electrical quantities cannot be directly accepted by subsequent display, recording, and analysis instruments. Therefore, sensors with different electromechanical conversion principles must be equipped with dedicated measurement circuitry. The function of the measurement circuitry is to convert the sensor's output electrical quantity into a general voltage signal that can be accepted by subsequent display and analysis instruments.
