WrkShopNo02 Flashcards
What are the frequency units?
CPM: cycles/minute
Hertz: cycles/second
Orders: multiples of operating speed
What are the amplitude units of vibration?
Displacement: mils-peak to peak (1,000 mils = 1 inch)
Velocity: in./sec-peak or rms (root mean square)
Acceleration: Gs peak (386.1 in./sec squared)
What is the physical nature of vibration?
Response to one or more time-varying force that may or may not be normal.
What factors govern the amount and frequency of vibration?
Process of the machine
Manufacturing and installation
Defects in machine components
What are the units of displacement and acceleration?
Displacement: mils-peak to peak (1,000 mils = 1 inch). Used at less than 600 CPM or 60 Hz.
Acceleration: Gs Peak, RMS (Root Mean Square), (386.1 in/sec squared = 1 Gravity), Used at more than 60,000 CPM
What do non-contacting displacement sensors measure?
They measure shaft vibration relative to the mounting position of the probe. (mils peak to peak)
What are the units of electrical signals obtained from vibration sensors?
The units of the electrical signal are volts or millivolts. (1,000 mv = 1 volt)
Define period and frequency of vibration.
The period is defined as the time required to complete one cycle of vibration. (Seconds per cycle)
The frequency is defined as the number of cycles or events per unit time. (Cycles per second (HZ) or Cycles per minute (CPM))
What are the units of period?
Seconds per cycle (or) milliseconds per cycle.
What is a measure?
Displacement: stress
Velocity: fatigue
Acceleration: force
What are the common vibration measures?
Displacement
Velocity
Acceleration
What is a spectrum?
A spectrum is a way to view a waveform using amplitude vs frequency.
How are peak amplitude units changed to RMS?
Multiply the peak value by 0.707 when the waveform is harmonic.
What is excitation and what does it do?
Excitation is a force that acts on a component and causes vibration.
What is the one most important frequency measured in a machine?
Operating Speed
