Vibration sensors are sensors for measuring, displaying, and analyzing linear velocity, displacement and proximity, or acceleration.

Vibration — however subtle and unnoticed by human senses — is a telltale sign of machine condition. Abnormal vibration indicative of problems with an industrial machine can be detected early and repaired before the event of machine failure; because such a failure is potentially costly in terms of time, cost, and productivity, vibration measurement allows industrial plants to increase efficiency and save money. Therefore, vibration analysis is used as a tool to determine equipment condition as well as the specific location and type of problems.

The severity of machine vibration is standardized by the International Standards Organization (ISO) in the ISO 10816 publication. The standard describes acceptable vibration levels for four different classes of machines. This data, as laid out in the chart below, proves useful as a reference point when analyzing vibration measurements.

Guide to vibration severity per ISO 10816

Form Factor and Construction

This page classifies various devices — including sensors (or transducers), transmitters, and switches for vibration measurement — under the blanket term "vibration sensor." Many devices which are not nominally considered vibration sensors can be used for vibration measurement; for example, Accelerometers Specification Guide are frequently used to measure vibration as well as acceleration. Basic vibration sensor types are described below.

• Vibration sensors are simply packaged as a raw sensor.
• Vibration transducers are slightly more complex sensors which output a voltage or current signal.
• Vibration transmitters are sensors packaged with the means (such as integral signal conditioners) to transmit a more complex output.
• Vibration switches use an integral sensor to make or break contact when certain vibration levels are detected.

A typical raw vibration sensor. This device would include a connector to allow transmission of an output signal.

The ISO 10816 is one of the most important vibration measurement standards and is described in more detail below.

Applications and Industries

The table below describes the industries which commonly use vibration measurement, as well as the product traits for sensors designed for each. The unique characteristics of each industry determine ideal sensor characteristics; for example, the very slow rotation of turbines in the mining and wind power industries results in the use of a vibration sensor with a very low frequency response of around 1 Hz or less. In contrast, the oil and gas industry requires high frequency (greater than 10 Hz - 10 kHz) sensors to cope with the faster rotation of turbines and gears.

Standards

Standards related to vibration measurement are published and maintained by numerous standards bodies. Examples of these include:

ISO 4866 -- Mechanical vibration and shock - Vibration of fixed structures - Guidelines for the measurement of vibrations and evaluation of their effects on structures.

AS 2625.1 -- Mechanical vibration - Evaluation of machine vibration by measurements on non-rotating parts Part 1: General guidelines

References

National Instruments - Vibration Sensors

Image credits:

PCB Piezotronics | Reliability Direct | Carleton University