The working principle of a digital handheld vibration meter is to convert the mechanical quantity of vibration into electrical signals through sensors, and then process and calculate the data through circuits to visually display the acceleration, velocity, displacement and other parameters of vibration in digital form. The core is to achieve the conversion of "mechanical vibration → electrical signal → digital result".
The workflow is mainly divided into four core steps, which work together to ensure measurement accuracy and convenience:
1. Vibration signal acquisition: Sensors convert mechanical vibrations into electrical signals
This is the core input link of the vibration meter, which mainly relies on the built-in piezoelectric sensor (currently the mainstream type). The principle is as follows:
The piezoelectric crystals (such as quartz and piezoelectric ceramics) inside the sensor have a "piezoelectric effect": when the probe of the vibration meter contacts a vibrating object, the vibration of the object will drive the piezoelectric crystal to undergo mechanical deformation.
Deformation can cause the surface of piezoelectric crystals to generate equal amounts of charges with different signals, forming a weak alternating voltage signal (electrical signal), and the frequency and amplitude of the electrical signal correspond linearly with the frequency and intensity of the object's vibration (the stronger the vibration, the larger the amplitude of the electrical signal).
Some vibration meters may be equipped with magnetic or probe type probes to ensure close contact with the object being measured and reduce signal loss (such as for vibration measurements in small devices or confined spaces).
2. Signal preprocessing: amplification and filtering, eliminating interference
The electrical signals output by sensors are usually weak (at the millivolt or even microvolt level) and may contain environmental interference (such as electromagnetic noise), which needs to be processed through internal circuits:
Signal amplification: Amplify weak electrical signals to a manageable voltage range (usually in volts) through an operational amplifier, providing a stable signal source for subsequent processing.
Filtering processing: Built in low-pass, high pass, or band-pass filters are used to filter out interference signals unrelated to measurement (such as high-frequency electromagnetic noise and low-frequency environmental vibration), retaining only effective signals related to object vibration to avoid measurement errors caused by interference.
3. Signal Conversion: Convert analog signals to digital signals
The preprocessed electrical signal is still an analog signal (continuously changing voltage) and cannot be directly processed by digital circuits. It needs to be converted through the following steps:
The A/D converter (analog-to-digital converter) inside the vibration meter will "sample" the analog electrical signal at fixed time intervals, converting the voltage value of each sampling point into a corresponding digital code (binary data).
The sampling frequency must meet the Nyquist criterion (usually more than twice the frequency of the measured vibration) to ensure that the digital signal can fully restore the characteristics of the original vibration and avoid signal distortion.
4. Data operation and display: outputting intuitive numerical results
After being processed by a processor, the digital signal is finally presented in a user readable form:
Data calculation: The processor converts the voltage value corresponding to the digital signal into physical parameters of vibration based on a preset algorithm (combined with sensor sensitivity parameters), such as acceleration (unit: m/s ², g), velocity (unit: mm/s), displacement (unit: μ m) - these three parameters are the core indicators of vibration measurement and can be switched for display according to needs.
Digital display: The calculation results are directly displayed in digital form on the LCD screen. Some models also support waveform charts, maximum/minimum/average value statistics, or switching units and storing data through buttons for easy on-site recording and subsequent analysis.