Vibration can generally be expressed in the following three units: mm, mm/s, mm/ S2.  
 
Amplitude, vibration velocity (vibration velocity), vibration acceleration.  
 
Amplitude is the representation, velocity and acceleration is the degree of rotor excitation force.  
 
Mm vibration displacement: generally used for low speed machinery vibration assessment;  Mm /s vibration speed: generally used for vibration evaluation of medium speed rotating machinery;  
 
Mm/S2 vibration acceleration: generally used for vibration evaluation of high-speed rotating machinery.  
 
The practical engineering vibration velocity is the effective value of velocity, which represents the energy of vibration.  Acceleration is the peak value, representing the magnitude of the impact force in the vibration.  
 
Amplitude is understood as distance in mm;  The vibration speed is understood as the speed, in mm/s.  The acceleration of vibration is understood as the acceleration of motion in mm/s2.  Speed describes how fast you move;  Vibration velocity is how fast it vibrates, how much amplitude it can produce in one second.  The vibration state of equipment with the same amplitude may be different, so the vibration velocity is introduced.