Measurement Computing Medallion Rotate rev.2.3 - Manual (Page 31)

October 2000 Medallion Rotate Manual
31
C
OMPUTED
O
RDER
T
RACKING
Computed Order Tracking uses the smooth speed curve from processing a
tachometer signal or from the RPM from Waterfall function. You can combine
the speed curve with data from a correlated transducer to perform a Computed
Order Tracking analysis. The correlated transducer can be an vibration sensor
(accelerometer, velocity sensor, non-contact probe) or any other meaningful
sensor (temperature, thickness, pressure, …).
A
PPLICATIONS
Computed Order Tracking shows you the amplitude and phase of the data
at selected orders, plotted against the machine’s speed. Computed Order
Tracking is ideal for variable speed machinery. This is particularly useful in the
following applications:
• Analyzing of the machine’s behavior during run-up or coast-down.
• Analyzing of a machine’s response to speed or load variations.
• Determining the frequency and severity of resonances, such as shaft
critical speeds, even when the resonances are heavily damped.
• Balancing rotors.
• Generating operating deflection shapes. For more on operating
deflection shapes, see “Exporting Calculated Orders Data to
ME’scope.”
I
NPUT
S
IGNAL
R
EQUIREMENTS
Medallion Rotate Computed Order Tracking requires a smooth speed curve
from processing a tachometer signal or using the RPM from Waterfall function.
Medallion Rotate processes the machine speed with the transducer data to
create the plot of the orders. When collecting the non-tachometer data
(vibration, temperature, …), note the following:
• If you want to see low frequency data in the Order Track plot, make
sure that the high pass filter setting in your analyzer is not excluding
the desired low frequencies.
• The sample rate in the analyzer must be at least 2.5 times the maximum
frequency of interest to avoid aliasing. Be aware that the anti-aliasing
filter in many data collection instruments truncates the upper 20-30% of
the frequency range (the highest orders in the signal).
• The choice of window function for analysis depends on the type of
resolution you need (amplitude or frequency resolution).