CoCo-80 User Manual
50
that Run/Hold is independent of Record/Stop. This means that when in Run
mode signals are not recorded to memory until the Rec./Stop button is pressed.
The record status is indicated by the red record icon blinking at the top of the
screen during recording. It is important for you to understand the difference
between Run/Hold and Record/Stop so that operator errors are not made
when recording signals.
When in Hold mode, the signal analyzer will be held. Processing such as spectral
analysis will be frozen.
Display Window Types
Bode Plot
The term Bode Plot is borrowed from the field of control theory, referring to a plot
of magnitude and phase angle between the input and output verses frequency of a
control system. Many in the rotating machine vibration industry have adopted
this term to describe the steady-state vibration response amplitude and phase
angle versus rotational speed (RPM). It turns out that the Bode Plot is the best
way to describe order tracks with phase. Bode plots are typically used for
transient analysis in both start-up and coast-down conditions. A Bode plot
can help to identify the resonance speed of a rotor or examine the rotor
dynamics on an order basis.
In the CoCo system, after the order tracks are acquired together with their phase
information then the Bode Plot can show one or multiple tracks.
Nyquist Plot
The Nyquist Plot shows real and imaginary values of a Frequency Response
signal. The signal is plotted parametrically in frequency, with a red line showing
the real and imaginary values over the frequency range. Real values are plotted in
the horizontal axis and imaginary values in the vertical axis.
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