Select repeatable measurement points
Measurement positions should be physically marked or documented so that trend values remain comparable. Bearing housings and radial or axial directions are selected from machine design and expected faults.
- Bearing location
- Measurement direction
- Sensor mounting method
- Machine speed and load
Use the correct vibration quantity
Acceleration is sensitive to higher-frequency behaviour, velocity is widely used for overall machine vibration, and displacement is relevant for lower-frequency shaft or structural motion. Derived units require appropriate integration and filtering.
- Acceleration in g or m/s²
- Velocity in mm/s RMS
- Displacement in μm
- Frequency-band values
Combine overall trend with diagnostic data
Overall values make change visible, but time waveform and FFT help explain the change.
- Overall RMS and peak
- Time waveform
- FFT spectrum
- Crest factor and other indicators
- Speed and process state
Design alarm logic carefully
Thresholds should be selected from machine class, baseline condition, operating state and maintenance objectives. Persistence and delay prevent short transient events from becoming repeated alarms.
- Warning level
- Danger level
- Persistence
- Hysteresis
- Acknowledgement
Preserve event evidence
When a threshold is exceeded, retain a timestamped diagnostic record and the machine state. This makes later review much more useful than a simple notification.
- Pre-event and event measurement
- Trend around event
- Waveform and spectrum
- Maintenance action
- Post-maintenance confirmation