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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
Averages on page
Rockwell Automation Publication 1441-UM001B-EN-P - September 2012
Fmax (CPM)
-------------------------------
Fmax (Hz)
=
60
spectral lines
------------------------------ -
collection time
=
Fmax (Hz)
7200 CPM
------------------------- -
=
60
400 lines
---------------------
=
3.3 seconds
120 Hz
80.
Setting Up Measurements
120 Hz
Number and Type of
Chapter 3
99
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