Measurement Computing Medallion Rotate rev.2.3 - Manual (Page 36)

36
Medallion Rotate Manual October 2000
and choose Properties. Then select the parameter for the cursor under
Track axis on the Cursor tab.
You can also use spline-fit machine speed curve produced by Tachometer
analysis to display the torsional orders.
1. Display the Channel List window.
2. Select the torsional file (*.tor) and the smoothed spline-fit file (*.spl).
and click the Computed Order Tracking button. For this example,
displaying the 1.0 and 1.5 orders
shows the firing order and the
imbalance. The upper curve on the
lower plot shows the firing order,
and the lower curve shows the
imbalance. Note the amplitude of
the firing order curve decreases
with increasing speed.
3. Running the Computed Order Tracking again using more orders, and
setting the X axis to frequency shows all the peaks lining up at the
resonant frequency.
T
HEORY
Torsional vibration causes small
variations in the speed of a rotating
component. These variations can be
detected in the speed signal from the
component, provided that the signal
provides sufficient resolution. Medallion
Rotate processes the speed signal, and converts the variations in speed to the
frequency domain. This generates a time history of the speed as a DC signal. If
the original tachometer signal contains N pulses/rev, Medallion Rotate can
extract torsional orders up to N/2 orders.