Rockwell Automation Publication 1441-UM001B-EN-P - September 2012 99
Setting Up Measurements Chapter 3
If your Maximum frequency is specified in CPM, convert CPM to Hertz using
this formula.
Next, find the total collection time for the time waveform measurement using
this formula.
If you had a Maximum frequency value of 7200 CPM and a Number of lines
value of 400, you would:
1. Convert CPM to Hz.
2. Find the total collection time.
Time Synchronous Averaging in the Dynamic 2500 Data Collector
Time synchronous averaging cancels out the effects of signals not related to the
synchronizing trigger. Time synchronous mechanical effects include imbalance,
misalignment, eccentricity of bent shafts, blade passing, and gear meshing.
Time synchronous averaging requires the internal laser tachometer or an external
trigger input to the data collector.
Set up a collection specification with the averaging Type set to Time
Synchronous and enter the Number of averages. Use a large number of averages
(such as 20 or 30) to get the desired reduction in non-synchronous effects.
For more on supported averaging in the data collector, see Number and Type of
Averages on page 80.
Fmax (Hz)
Fmax (CPM)
60
-------------------------------
=
collection time
spectral lines
Fmax (Hz)
-------------------------------
=
7200 CPM
60
--------------------------
120 Hz=
400 lines
120 Hz
---------------------
3.3 seconds=
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