Rockwell Automation 1441-PEN25-Z Enpac 2500 Data Collector - Manual (Page 71)

Rockwell Automation Publication GMSI10-UM002D-EN-E - August 2012 71
Setting Up Measurements Chapter 2
Measurement Window Types
The measurement window type is part of the collection specification (Setup >
Collection
). See Setting Up Collection Specifications on page 69 . You select the
collection specification when you set up the measurement definition.
Emonitor and the Enpac 2500 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.
• 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.
Measurement Signal Detection Types
The signal detection is part of the collection specification (Setup > Collection).
See Setting Up Collection Specifications on page 69 . You select the collection
specification when you set up the measurement definition.
Emonitor and the Enpac 2500 support the following signal detection types.
• 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.
• Peak - Use for detection of acceleration, velocity, and high frequency
energy. This is the peak (0 to maximum) amplitude of a sine wave at the
frequency of interest and is calculated from the RMS value.
• Peak-Peak - Use for detection of displacement; sometimes used for high
frequency energy. This is the peak-to-peak (minimum to maximum)
amplitude of a sine wave at the frequency of interest and is calculated from
the RMS value.