Collect a Filtered Orbit

 

Prerequisites

Ensure all sensor inputs use the same data units.

Overview

Filtered Orbit lets you analyze the phase relationship between two or four channels at a specific order of turning speed. Orbit plots show the relative movement of a rotating shaft with respect to some reference point.
Note: Filtered Orbit is only available for the two and four channel analyzer. For orbit plots, the analyzer uses the lowest input channel for the X axis and the next input for the Y axis. For a two-channel orbit using inputs A and C, A =X and C= Y. If you use inputs B and D, B=X and D=Y. For a four-channel dual orbit, A=X1, B=Y1, C=X2, and D=Y2. A and B are used for the first orbit, and C and D are used for the second orbit.

You can create orbit plots using normal two-channel or four-channel route data, but you must set up the acquisition to collect the correct amount of data. Also, filtering is not included. Filtered Orbit eliminates the complicated setup. Filtering the data lets you arrange the orbit’s parameters so only certain frequencies are included in the orbit plot, and the pattern is easier to recognize.

Procedure

  1. Create a job.
  2. From the Analyze main menu, press F1 Manual Analyze > F1 Set Analyze Mode.
  3. Use the up and down arrow keys to select Filtered Orbit.
  4. Press Enter.
    The Analyze Setup screen appears.
  5. Set the following options as necessary.
    Option Description
    F2 Orbit Mode Select Bandpass or Lowpass. For Bandpass, the analyzer calculates peak and phase data for both channels using a tachometer input, creates two waveforms, and plots these values in the X (horizontal) and Y (vertical) directions. The orbit plot is a representation of a band pass filtered signal. The band pass orbit includes the energy for all frequencies within the specified bandwidth centered around the specified RPM times orders value.

    For Lowpass, the analyzer includes all frequencies at and below RPM times orders. The analyzer does low pass filtering on the data as it is collected. All frequencies above the “orders times RPM” value are filtered out when the waveforms are collected. The actual collected waveform data are plotted in the orbit. Since this method creates a plot that includes all frequencies from the desired order level and lower, it will show more complex orbits that can indicate rubs, misalignment, or oil whip. The default is Lowpass.

    F3 Set Order Select 1x, 2x, or 3x order of the shaft turning speed. The default is 1X.
    F4 Set Revs. For Lowpass mode, enter a value between 1 and 99 to set the number of revolutions to display in the orbit plot. The default is 1.
    F4 Set Bandwidth For Bandpass mode, enter a value between .02 and 1.0 to set the bandwidth of the tracking filter to attenuate all frequency components, except the desired peak. The bandwidth of the filter is the frequency of the peak multiplied by the bandwidth parameter. A lower (more narrow) filter attenuates frequency components that are close to the desired peak. The default is 0.1xRPM.
    F7 Tach Setup Set up the tachometer parameters. See Set up a tachometer in Analyze.
    F8 Use Tach (Appears only in Lowpass mode.) If a tachometer is not used, the filter is set based on manual RPM entry. If a tachometer is used, the filter is constantly updated for changing machine speeds and the orbit is phase related to the sensor. The default is Yes.
    F9 Set RPM Appears only when Use Tach is set to No. Enter a value between 300 and 18,000 to the machine RPM. The default is 3,600.
    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.