KutupASP DijitalFor a sinusoid, the acceleration amplitude equals 2πf times the velocity amplitude, and velocity equals 2πf times displacement. So acceleration suits high-frequency faults such as bearings and gears, velocity suits overall machine condition, and displacement suits large, low-frequency motion. The right choice depends on the purpose of the measurement.
Vibration is the repeated movement of a point about its rest position. It can be measured as displacement (micrometers, µm), velocity (mm/s) or acceleration (m/s² or g). Velocity is the time derivative of displacement, and acceleration is the time derivative of velocity.
For a sinusoidal motion, the acceleration amplitude is 2πf times the velocity amplitude, and the velocity amplitude is 2πf times the displacement amplitude. As frequency rises, the same motion looks larger in acceleration and smaller in displacement. That is why an accelerometer picks up high-frequency faults well, while displacement measurements track large, low-frequency motion.
Velocity is widely used for overall machine condition. The ISO 20816 series, for example, usually evaluates velocity RMS values. Which quantity to use is decided by the standard and by the purpose of the measurement.
Consider a hypothetical measurement: a sinusoidal vibration at 100 Hz with a peak velocity of 10 mm/s.
These numbers hold for one sinusoid only. A real machine has many frequencies at once, so each component must be converted on its own. Converting the total band value can be misleading.
Three mistakes are common:
In theory yes, in practice it needs care. Low-frequency noise and DC offset grow when you integrate. Apply a suitable high-pass filter first, or use a velocity sensor directly. In the frequency domain, multiplying each component's amplitude by 1 / (2πf) is another way.
It depends on the purpose. Displacement suits large, low-frequency motion and shaft movement. Velocity suits overall machine condition and comparison with standards. Acceleration suits high-frequency faults such as bearings and gears. Use whichever quantity your measurement standard specifies.
Example numbers are hypothetical, not measured field results.
After reading, you can track a machine's broadband vibration against its own baseline and read the ISO 20816 zones in the right context, without treating a zone as a fault diagnosis.
Data from a vibration sensor cannot be interpreted without knowing which quantity it measures, which frequency range it sees and how it was mounted.
