Methods to Describe Vibration
An engineer can identify something erratic in equipment by feeling the heat, or by listening to the noise, or by watching the device's status. It may vary person to person. Therefore the vibration analyst should put his faith in reliable methods that produce written data.
Amplitude and Frequency are measurable parameter to describe the vibration.
Amplitude: Severity of Vibration
Amplitude describes the amount of vibration noted on the object. More movement means more criticality of the object condition. Velocity or speed shall be measured in a specific direction in terms of peak value or rms (root-mean-square) value. Its unit is in/s or mm/s.
Vibration data shall be displayed in the form of trend called the waveform. Example trend of velocity waveform: Click here velocity waveform
At given time how fast the object movements take place is displayed in graphical waveform. Vibration analysts shall measure velocity data for specified time period and should carry out analysis accordingly.
Frequency: Oscillation rate of Vibration
A machine may oscillate fast or slow depending on the vibration. The rate of machine part oscillation is called the vibration frequency. The number of oscillation cycles per second is defined as the frequency, e.g. 3 cycles per second (Hertz) or 3 cycles per minute.
Spectrum: It is combination of the frequency of component vibration and velocity amplitude measured at that time. Click for trend overview: spectrum trend
The velocity spectrum of a vibrating machine indicates at “X" speed the object is vibrating with “Y" frequency. For example, the equipment is vibrating at a frequency of 75 Hz with an velocity amplitude of 10 mm/s. Considering both the frequency and related amplitude, we can find out the cause of the vibration and the machine health.