Types, advantages and disadvantages of vibration sensors and vibration transmitters

# Types, Advantages and Disadvantages of Vibration Sensors

Accidents caused by mechanical vibration have become increasingly prominent in large rotating machinery such as wind turbines, steam turbines, water turbines, compressors, water pumps and electric motors. Therefore, vibration measurement has become an indispensable and critical part of rotating machinery monitoring. This article introduces the types, advantages and disadvantages of vibration sensors, so that appropriate sensors can be selected for vibration testing. Proper sensor selection can not only achieve satisfactory test results and save labor and time, but also play a vital role in quickly identifying the root causes of vibration faults, improving rotor balancing accuracy and reducing machine start-stop cycles.

Based on working principles, vibration sensors fall into five categories: magnetoelectric, eddy current, piezoelectric, capacitive and inductive sensors. The latter two are rarely used nowadays due to severe interference from surrounding media and will not be discussed herein.

## Magnetoelectric Vibration Sensors

1. Easy to install and adaptable to the environmental conditions of most machinery.

2. No external power supply is required, and vibration signals can be transmitted to target locations without preprocessing.

## Eddy Current Sensors

### Advantages

1. The output signal is proportional to vibration displacement, delivering strong output signals for most machinery where vibration conditions are characterized by amplitude.

2. Directly measures shaft vibration and supports both static and dynamic measurement, compatible with most machinery operating environments.

3. Simple structure and compact size; it features a suitable frequency response range for steam turbine generator unit vibration and allows convenient calibration.

4. Beyond vibration measurement and static component position detection, it can measure shaft center position, shaft center movement trajectories during startup, bearing center displacement, etc. It can also serve as a key phase signal for rotational speed and vibration phase measurement.

### Disadvantages

An external power supply is mandatory. Installation procedures are complicated with stringent requirements, and a preamplifier must be matched (Note: Integrated all-in-one sensors are now available).

The linear range and sensitivity of the sensor vary with the material of the measured vibrating object, requiring recalibration in such cases.

## Piezoelectric Vibration Sensors

### Advantages

1. Small size and light weight, suitable for certain vibration test systems highly sensitive to additional mass load.

2. Features a much wider response frequency range (4 Hz to 2000 Hz) than magnetoelectric velocity sensors, with mechanically robust internal moving parts that are less prone to damage.

### Disadvantages

Measurement results are greatly affected by installation methods and wiring layout. Its operating frequency range is excessively high for steam turbine generators, and calibration is difficult.