Text: The repetition rate of a periodic vibration within a unit time. This is normally expressed in units of cycles per minute (cpm), events per minute (epm), or cycles per second (cps or Hz). It can be expressed relative to shaft rotative speed. With respect to rotating machinery vibrations, there are two types of frequencies of interest: A) the shaft rotative frequency, and B) the various vibration frequencies as measured by vibration transducers. Rotative frequency is usually expressed in terms of rpm. Vibration frequencies are commonly expressed in terms of a fraction or percentage of the shaft rotative frequency: 1X means one times rotative frequency, 2X means two times, 1/2X, or 50 percent, means one-half times, etc. Field of Rotating Machinery Measurment, Monitoring and Analysis Frequency = the number of cycles per TIME Wave Number = the number of cycles per SPACE

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