Accelerometer

An instrument for measuring acceleration, as of aircraft or guided missiles.

The most common type is probably the piezoelectric accelerometer which is widely used in the measurement of machinery vibration. The output is usually produced by force applied to a piezoelectric crystal which generates a current proportional to the applied force. This current is then amplified and displayed as a time waveform or processed by a Fourier transform to produce a frequency display. Single integration of the acceleration signal will produce a velocity display and double integration of the acceleration signal will produce a displacement display.

A wide range of accelerometers of different types and sizes are commercially available to cover the many different applications in which they are used.

It is important when choosing an acceleromter to consider the sensitivity and range that the accelerometer will operate over for the application.

• Ensure the frequency that is being investigated is within the usable range of the accelerometer
• Make sure that the maximum capable amplitude of the accelerometer is not exceeded at any point during the test.

Mounting

There are a number of ways that an accelerometer may be attached to the structure to be measured.

Bolted

Wax

Superglue

Hot melt glue

Accelerometers are probably the most widely used transducers in any investigation work on a structure of any kind. NVH (Noise, Vibration & Harshness) testing is just one of many fields that make use of them. If there is a requirement to find the frequency of a vibration, for example, an accelerometer would be the obvious choice.

See also: Laser Vibrometer, Velocity Transducer.

Further reading:
• Handbook of Modern Sensors, Jacob Fraden, Springer-Verlag Berlin and Heidelberg GmbH & Co. KG

Weblinks:
• Bruel & Kjaer - Technical Reviews These documents give detailed articles on measurement and signal processing theory.