Predictive Maintenance · Vibration · Accelerometers · Rotating Equipment
Vibration Sensor Working Principle: 4 Vital Facts for Rotating Equipment Health
A bearing rarely fails without warning, it vibrates differently for weeks before it actually breaks. This guide explains the vibration sensor working principle behind accelerometers and proximity probes, walks through the ISO 10816 severity chart, and includes a video and a live vibration severity calculator.
Why Vibration Is an Early Warning Signal
Every piece of rotating equipment vibrates to some degree, and that vibration signature changes long before a failure actually happens. Imbalance, misalignment, bearing wear, and looseness all show up as changes in vibration amplitude and frequency well ahead of a breakdown, which is exactly why vibration sensors sit at the center of predictive maintenance programs on motors, pumps, fans, and turbines.
Two very different sensor technologies dominate this space. Accelerometers measure vibration by physically moving with the equipment casing, while proximity probes measure shaft position without ever touching it, and the right choice between them depends heavily on how the machine is actually supported.
4 Vital Facts About Vibration Sensor Working Principle
The Main Vibration Sensor Types
These four designs cover nearly every real world application of the vibration sensor working principle you will encounter.
Measures vibration through the charge generated when an internal mass presses on a piezoelectric crystal, mounted directly on the machine casing.
Best suited for: rolling element bearings on motors, pumps, and fans.
A micromachined silicon structure changes capacitance as it moves, offering a compact, low power alternative to piezoelectric designs.
Best suited for: low frequency, portable, and wireless monitoring applications.
Generates an electromagnetic field and measures the gap to a conductive shaft based on induced eddy currents, without any physical contact.
Best suited for: turbines and compressors on fluid film bearings.
Traditionally used a coil and magnet to directly generate a voltage proportional to velocity, though many modern versions integrate an accelerometer signal instead.
Best suited for: general purpose overall vibration monitoring.
ISO 10816 Vibration Severity Zones
Watch: Turbine Vibration Monitoring System Explained
This short video explains how a vibration monitoring system protects rotating machinery such as turbines.
Relating Acceleration, Velocity, and Displacement
Displacement = Velocity / (2πf)
Where:
f = vibration frequency in Hz
Acceleration is typically measured directly by an accelerometer
Velocity and displacement can be derived through integration
Example: Acceleration 2 g (19.6 m/s²) at 50 Hz Velocity = 19.6 / (2 × 3.1416 × 50) ≈ 0.0624 m/s ≈ 62.4 mm/s Acceleration is usually preferred for high frequency bearing defects, velocity is the standard basis for ISO 10816 severity charts, and displacement is typically used for shaft position monitoring on fluid film bearings.
Accelerometer vs Proximity Probe
| Feature | Accelerometer | Proximity Probe |
|---|---|---|
| Contact with machine | Mounted on casing | Non contact, measures shaft directly |
| Typical bearing type | Rolling element bearings | Fluid film (journal) bearings |
| What it measures | Casing vibration (acceleration) | Shaft displacement and position |
| Common application | Motors, pumps, fans | Turbines, large compressors |
Where Vibration Monitoring Is Used
Applying the vibration sensor working principle correctly protects a wide range of rotating and structural equipment.
Early detection of bearing wear before a costly unplanned motor failure.
Vibration trends reveal cavitation, imbalance, and misalignment issues early.
Proximity probes provide continuous shaft position and vibration protection.
Critical rotating equipment relies on continuous vibration based protection systems.
Accelerometers track building and bridge movement during seismic or wind events.
Power generation equipment depends on early vibration trend detection for reliability.
Applying Vibration Monitoring Correctly
Getting the vibration sensor working principle right in practice comes down to a few consistent field habits.
- Match sensor type to bearing design: accelerometers for rolling element bearings, proximity probes for fluid film bearings.
- Trend readings over time: a rising trend often matters more than any single absolute reading.
- Check the correct ISO 10816 or 20816 sub part: for your specific machine class and mounting type.
- Mount sensors securely and consistently: a loose sensor introduces its own false vibration signal.
- Don't rely on casing vibration alone for fluid film bearings: the casing often shows far less movement than the shaft itself.
- Don't ignore mounting quality: a poorly attached sensor or loose cable can distort the real signal.
- Don't compare overall vibration across different machine classes: the same reading can mean very different things.
- Don't skip spectral analysis when overall levels rise: frequency content usually reveals the actual root cause.
Vibration Velocity to ISO 10816 Zone Checker
Enter a measured vibration velocity to check which illustrative ISO 10816 zone it falls into for a small, Class I machine.
Quick FAQs: Vibration Sensor Working Principle
External References
- Wikipedia: Accelerometer
- ISO 20816: Mechanical Vibration, Measurement and Evaluation of Machine Vibration
- Baker Hughes Bently Nevada: Vibration Monitoring Systems
What we learn today
- Vibration sensor working principle differs fundamentally between contact accelerometers and non contact eddy current proximity probes.
- Bearing type, rolling element versus fluid film, usually decides which sensor technology actually fits an application.
- ISO 10816 and its successor ISO 20816 define severity zones based on machine class, not a single universal number.
- Frequency content, not just overall vibration level, usually reveals the real root cause behind a developing machine fault.