What is vibration monitoring in maintenance, and what are common measurement types and units?

• A. Monitoring equipment condition using motion sensors; measurements include acceleration (g or m/s²), velocity (mm/s), and displacement (µm).
• B. A method to measure ambient sound levels in the facility.
• C. A diagnostic for electrical insulation resistance.
• D. A technique for optical alignment.

Answer: (C)

Vibration monitoring focuses on checking machine condition by watching how parts move during operation with motion sensors. The data collected describe how vibration energy is distributed over time and frequency, and the common measurements are acceleration, velocity, and displacement. Acceleration is usually expressed in g’s or meters per second squared (m/s^2). Velocity is measured in millimeters per second (mm/s). Displacement is given in micrometers (µm) or mils. Each type highlights different fault characteristics: acceleration captures high-frequency content often linked to bearing faults and looseness, while velocity and displacement emphasize lower-frequency motion associated with imbalance, misalignment, or structural looseness. In practice, accelerometers are widely used for general condition monitoring because they provide rich spectral data and quick response to changes. The other options describe different diagnostics not focused on mechanical vibration: ambient sound level checks relate to acoustics, insulation resistance covers electrical insulation health, and optical alignment concerns the positioning of components. Vibration monitoring, using motion sensors and these measurement types/units, is the standard approach for assessing mechanical health.