Rockwell Automation 1441-DYN25-Z Dynamix 2500 Data Collector - Manual (Page 77)

Rockwell Automation Publication 1441-UM001B-EN-P - September 2012 77
Setting Up Measurements Chapter 3
Measurement Window Types
The measurement window type is part of the collection specification (Setup >
Collection). Select the collection specification when you set up the measurement
definition.
The Emonitor software and the Dynamix 2500 data collector support the
following measurement window types. In general, the Hanning measurement
window provides the best compromise of frequency and amplitude accuracy for
most predictive maintenance measurements.
Measurement Signal Detection Types
The signal detection is part of the collection specification (Setup > Collection).
See
Collection Specification Dialog Box on page 75 . You select the collection
specification when you set up the measurement definition.
The Emonitor software and the Dynamix 2500 data collector support the
following signal detection types.
Measurement
Window Types Description
Hanning A general purpose window to use on random type data when frequency
resolution is more important than amplitude accuracy. Use this setting
for most of your machinery monitoring activities.
Rectangular The data collector does not apply a window. Use this only for transient
signals that die out before the end of the time sample, or for exactly
periodic signals within the time sample.
Flattop Use this when amplitude accuracy is more important than frequency
resolution. In data with closely spaced peaks, a Flattop window may
smear the peaks together into one wide peak. Use this setting for
sinusoidal or calibration signals.
Hamming A general purpose window that is similar to the Hanning window. It
provides better frequency resolution but decreased amplitude accuracy
when compared to the Hanning window. You can use it to separate close
frequency components.
Table 21 - Signal Detection Types
Signal
Detection Type Description
None Use for numeric measurements. None defaults to RMS when applied to
magnitude or spectrum measurement definition.
RMS Use for detection of voltage and current. For the frequency domain, the dynamic
signal is measured as the square root of the mean of the square of the signal.
This is the RMS amplitude of a sine wave at the frequency of interest. For the
time domain, the dynamic time signal is squared, integrated over some time
period, and then the square root is taken.