For rotating equipment

Acceleration and velocity of a vibration are the result of displacements with time

Peak velocity is proportional to displacement and frequency

Vpeak = 2Pf*(peak displacement)

Peak acceleration is proportional to displacement and frequency squared

Apeak = 4*(P^2)*(f^2)*(peak displacement)

Energy is proportional to frequency and amplitude

Examples

Fan Motor

30 Hz (1800 RPM) with a displacement of 1mm peak

Velocity = 0.2m/s

Acceleration = 35.5 m/s^2 = 3.62g peak

Turbine

10,000 Hz with a displacement of 0.0001mm peak

Velocity = 0.006m/s

Acceleration = 394m/s^2 = 40g

Notice how high frequencies combined with small displacements cause large acceleration

Even low energy inputs applied to an absolutely fixed accelerometer can cause very large acceleration (this is common to all accelerometers)

Many applications can tolerate a small amount of "cushioning" of the accelerometer to protect it from damage due to exposure to very large acceleration (cushioning acts as a low pass filter)