Section 4 — Measurement Types and their Uses
84
The sensors used to take the measurements should be displacement
probes. This is because we are measuring the physical movement of the
shaft, not its speed. (You can take the readings with an accelerometer if
no displacement probes are available but there will be a small loss of
accuracy in the displayed plot when the signals are integrated.) The
number of samples and measurement duration you choose determines
the resolution and length of the orbit recording. We suggest 1024
samples and a duration that covers 4-6 revolutions of the machine
being tested. For example, an 890 RPM system (14.8 Hz) has 1 revolution
every 67 milliseconds (6 x 67ms = 402 ms). If you choose 400 ms for the
duration, you will just capture 6 revolutions of the machine.
NOTE: Severe rub or looseness can produce random orbit plots.
Once the recordings have been received in Ascent, you can select a
recording from either location > Select Chart > Orbit+Waveform. The
recording at the other location is automatically selected for plotting
when you choose the orbit plot option.
NOTE: If you have modified the legacy Orbit chart, this might also
display on the Chart menu
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