**Vibration Test Basic Knowledge - The Terms of Vibration Test**

Displacement - The distance that a vibrating mass moves.

Peak displacement, center-to-peak

Peak-to-Peak is the distance between the two farthest points of motion.

Units: Inches or Millimeters

Velocity - The speed at which the vibrating mass moves.

Units: Inches per second or Meters per Second

Acceleration - The rate at which the vibrating mass changes speed.

Units: "g" peak for Sine and Shock "Grms" for Random, Sine-on-Random, and Random-on-Ran

Frequency - The number of times an oscillation occurs in a period of time.

Units: Hertz (Hz) or Cycles per Second

Mass - The amount of matter contained in a body or product

Force - The applied energy causing motion or a change in motion

Units: Force Pounds (lbf) or Newtons(N)

Power Spectral Density(PSD) - Is a measurement of amplitude and frequency in a Random Vibration spectrum.

Units: Amplitude: (y axis) g2/Hz or (m/S2)2/Hz

Frequency - (x axis) Hertz (Hz)