Averaging minimizes the effect of random variations or noise spikes in vibration signals. When you measure vibration, several spectra are averaged to produce an average spectrum.
Depending on your measurement/mode in Manual Analyze, you can set the following:
- Number of averages to collect - Set the number of averages the analyzer acquires.
- Acquisition mode - Select Monitor mode to view live spectral data similar to a spectrum analyzer. In Monitor mode, the spectrum is instantaneous unless you use Peak Hold Average.
- Live plot - Select Instant Spectrum or Average Spectrum to view the last measurement or the average of all the measurements.
- Type of average - Set the method to calculate the average. The sections below list the type of averages available.
| Option | Description |
|---|---|
| Normal Average | Add the power in each frequency line and divide by the number of averages. Normal Average is suitable for most measurements. |
| Peak Hold Average | Display the largest amplitude of each spectral line. Use this option during a machine coast down or to monitor random fluctuations such as steam whirl or oil whirl. |
| Synchronous Time |
Remove the vibration of other machines from the signal, so only the vibration from the reference machine remains. The analyzer synchronizes each data sample with a tachometer pulse, computes the average, and creates the spectrum from the averaged waveform. Use Synchronous Time when you need data directly related to the turning speed of a specific shaft, or when several machines or shafts on one machine turn at slightly different speeds.Note: A tachometer is required with this mode.
|
| Order Tracking | Monitor machines where the speed is changing during data collection. Order Tracking helps normalize data so it does not look smeared. You must use a tachometer and a reference pulse. A tachometer pulse controls the data acquisition rate to account for variations in machine RPM. |
| Negative Average | Dynamically subtract one spectra from another while the machine runs. Negative Average reduces the number of spectra and compares the results with the results of a normal averaging or with bump test data to help isolate potential problems. The larger the number of spectra used for averaging, the more the noise spikes in vibration signals are reduced, and the more accurately true spectral peaks are represented. |
| Exponential Average | Average each new spectra with all prior ones
in the decay exponential form, where the rate of decay is set by the averages
value. A smaller average shows the vibration with a faster decay or rate of
change. Use this advanced method if vibration behavior varies significantly
during measurement.
Note: Do not use for routine data collection.
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