Collect a spectrum

 

Overview

A spectrum shows all of the frequencies and amplitudes of a machine, within the specified limits of the Fmax and Fmin values. The vibration spectrum is the basic tool for understanding vibration.

A vibration spectrum is a graph of vibration amplitude versus vibration frequency. The vibration spectrum shows the frequencies at which the component is vibrating and the amplitude of vibration at each of these frequencies.

Note: You can measure velocity in most situations. However, for low frequencies (below 1,800 cpm), displacement spectra are more informative. For high frequencies (above 60,000 cpm), acceleration spectra are more informative.

Procedure

  1. Create a job or open Analyze from a route measurement point.
  2. From the Analyze main menu, press F1 Manual Analyze > F1 Set Analyze Mode.
  3. Use the up and down arrow keys to select Spectra.
  4. Press Enter.
    The Analyze Setup screen appears.
  5. Set the following options as necessary.
    Option Description
    F2 Set Spectra Params Set the Fmax, Fmin, and lines of resolution. See Fmax and Fmin and Lines of resolution.
    F3 Set Averaging Set the type of averaging, the number of averages to collect, and the acquisition mode. See Averaging.
    F4 Set Window Set the type of window to use. See Windows.
    F5 Set SST/AWeight

    Enable F5 Set SST for very low frequency measurements. The model A0760GP is used down to 40 RPM. For frequencies lower than 40 RPM, contact Emerson for a recommendation.

    Enable F6 Set Aweight to apply a shape curve to the acquired frequency spectrum that approximates the frequency sensitivity of the human ear. A-weighting is used with microphone signals when you want to see perceived “loudness.” A high sensitivity, low frequency sensor is recommended. Use a general purpose accelerometer, such as part number A0760GP, for measurements as low as 40 RPM. Contact customer support for recommendations to measure lower frequencies.

    F7 Tach Setup Set up the tachometer parameters. See Set up a tachometer in Analyze.
    F8 PeakVue Demod Enable or disable PeakVue or Demodulation. See PeakVue and demodulation.
    F9 Set Trigger Select the type of trigger to use to start the measurement. See Triggers.
    F12 Input Setup Set up the input channels, the sensor type, and the units for the acquisition type.
  6. Press Enter to collect the data.
    One or more plots display the data.
  7. Press F9 Store Data to save the data to a route or a job, or press F8 Start to redo the measurement.