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C h a p t e r 2 | V i b r a t i o n S e n s i n g T e c h n o l o g y Vibration-based Faults and System Considerations Industrial machinery is vulnerable to various mechanical faults, each having its unique vibration signature. Imbalance, for instance, is marked by strong vibrations at 1x the motor's rate of rotation, along with a steady phase angle during rotation. In contrast, misalignment shows elevated vibrations at both 1x and 2x RPM, often accompanied by axial components. Bearing defects cause high-frequency vibration spikes and specific fault frequencies tied to bearing geometry. Conversely, gear defects lead to vibrations at gear mesh frequencies and sidebands, frequently accompanied by an increase in noise level. To accurately distinguish between these faults, condition monitoring experts rely on signal processing techniques such as spectral analysis, time waveform analysis, and envelope detection applied to accelerometer data. However, the success of fault diagnosis heavily depends on the quality of the acquired vibration data. Three critical characteristics of accelerometers determine their effectiveness in fault detection: 1. Low Noise: Lower noise allows for the detection of faults in their earliest stages, enabling timely intervention. 2. Wide Bandwidth: A wider bandwidth captures more comprehensive spectral content, improving fault classification accuracy. 3. High Measurement Range: Enables complete coverage for assets which generate larger vibrations. Evolution of Accelerometer Technology Traditionally, piezoelectric accelerometers have been the preferred choice for measuring high-frequency, low-noise vibrations in industrial settings. While they provide a wide dynamic range, their AC-coupled nature restricts their capacity to measure static acceleration. Enter MEMS (Micro-Electromechanical Systems) accelerometers, a technology that is transforming vibration monitoring. Modern MEMS accelerometers, exemplified by the ADXL1000 series, feature wide bandwidths up to 24 kHz, low noise density down to 25 µG/√Hz, and high sensitivity, matching the performance of piezoelectric devices in many industrial applications. Furthermore, MEMS accelerometers offer distinct advantages, including DC response, compact size, energy efficiency, and seamless integration into wireless and battery-powered systems, enabling flexible deployment in various monitoring scenarios. ADXL382: Advanced Triaxial Digital Sensor Among MEMS accelerometers, the ADXL382 is a triaxial digital wideband sensor designed for advanced condition-based monitoring applications. This sensor excels in three critical areas for effective fault detection: 1. Ultra-Low Noise: With noise levels below 55 µG/√Hz, the ADXL382 establishes a new standard for early fault detection capability. 2. Extensive Bandwidth: Its 8 kHz bandwidth ensures the capture of comprehensive spectral content, enabling accurate fault classification. 3. Ample Measurement Range: With a full-scale range of up to 60 G, the ADXL382 offers the SNR headroom necessary to comply with all four classes of the ISO2816 standard for vibration measurement. 7 Engineering Reliable Industrial Automation With Sensor Fusion