Different types of transducers are used to measure displacement, velocity, or acceleration. A displacement transducer is insensitive to the frequency of movement and only measures amplitude. A velocity transducer measures the result of amplitude multiplied by frequency. The small size, high output, and robustness of accelerometers has led to their use for measuring vibration velocity by converting the output in the instrumentation. The response of buildings to seismic events is a typical displacement application and low speed hydropower turbine vibration is another.
Acceleration is very suitable to high frequency conditions such as impact shock.
To obtain high frequency data, the mounting of the accelerometer is very critical since these small amplitude signals are severely attenuated at the mounting interface. The frequency range for most machinery falls in a middle range, and measurement of vibration severity in units of vibration velocity fits both the human response to vibration intensity and the effective machine condition. Vibration severity can be measured easily with a transducer that can be handheld, magnetically attached or screwed in position. A simple meter set up in accord with ISO 2372 can give an instant readout of vibration without the need to stop the machine. The readout of the vibration level provides a good indication of the machine condition.