Measurement-computing Medallion Rotate rev.2.3 Manuel d'utilisateur télécharger pdf (Page 29)

October 2000 Medallion Rotate Manual

RPM FROM WATERFALL

The RPM from Waterfall function in Medallion Rotate Plus allows you to

determine the machine speed from a waterfall file. If you do not have a

tachometer signal, or the signal is extremely noisy, you can use other data to

create an RPM curve that describes the speed of the machine over time.

Medallion Rotate can use this smoothed speed curve in the same ways as

a speed curve generated from a tachometer signal. You can use this speed

curve to diagnose some problems directly. You can also use the speed curve

along with other data, such as vibration, as an input for additional

sophisticated Medallion Rotate analysis techniques.

APPLICATIONS

The RPM from Waterfall function is applicable when you have a time

waveform from a data channel, but no tachometer signal or a noisy signal.

There may not be a tachometer available, or it may be impractical to use a

tachometer or other speed sensor on the machine. In some cases, the RPM from

Waterfall function may produce a better speed curve than a tachometer.

INPUT

When collecting the non-tachometer data (vibration, temperature, …), note

the following:

• If you want to see low frequency data in the Waterfall analysis, 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.

• The choice of window function for analysis depends on the type of

resolution you need (amplitude or frequency resolution). Since the

RPM from Waterfall function depends more on the position of the

spectral peaks than on the amplitude, the Hamming window is a good

default choice.

EXAMPLE

This example uses the RPMFromWaterfallDemo.wat file included with

Medallion Rotate Plus. You can also use any waterfall file generated by

Medallion Rotate using Waterfall analysis (see “Waterfall Analysis” ).

1. In the Channel List Window select

the RPMFromWaterfallDemo.wat

file, then select the waterfall

channel. You can display the

Waterfall by clicking on the Plot

button.

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Measurement-computing Medallion Rotate rev.2.3 Manuel d'utilisateur Page 29