Coast Down Peak and Phase


Coast Down Peak and Phase confirms resonance during a coast down, but requires tachometer input from the shaft turning speed. You want the operational vibration to excite the resonant frequencies in the system as the equipment coasts to a stop. The measurement records the amplitude and phase of the 1xRPM frequency. The results show a peak at any resonant frequency. At a resonance, the phase goes through a 180-degree phase shift.
Note: By default, the peak/phase coast down monitors the first harmonic of the turning speed. To perform the test on a different harmonic, use a cursor to mark a frequency before running Coast Down Peak and Phase.


  1. Create a job or open Analyze from a route measurement point.
  2. From the Analyze main menu, press F7 More Experts > F5 Coast Down Peak and Phase.
  3. Press Start or Enter to collect the data.
  4. Shut down the equipment.
  5. Press F3 Stop or F9 Stop when the equipment stops.
  6. Press Enter to view the data.
    One or more plots display after the data is collected.
  7. Press F9 Store Data to save the data to a route or a job, or press F8 Start to redo the measurement.