Rockwell Automation 1440-SDM02-01RA XM-124 Standard Dynamic Measurement Module - Manuel (Page 67)

Rockwell Automation Publication 1440-UM001C-EN-P - May 2014 67
Configure the XM-124 Standard Dynamic Measurement Module Chapter 2
Spectrum/Waveform Measurement Options
The Spectrum/Waveform Measurement options apply to the Standard,
Alternating gSE, Tracking Filter, Band Pass Filter, and Thrust Position
measurement modes. These settings affect the standard FFT and TWF
True The actual or literal measure of the signal. It is the maximum peak in the
time waveform for peak measurements, or the difference between the
maximum and minimum peaks for peak-to-peak measurements. The True and Calculated radio buttons are dimmed when full
scale is set to an RMS value.
For a pure sine wave, the true and calculated values are equal.
The true and calculated values diverge as additional signals
are added to the waveform, or as non-sinusoidal or non-
repetitive signals are included.
For protection applications where the objective is to preclude
contact between stationary and moving components, True is
the appropriate measurement because it is a better indication
of actual movement.
For conditioning monitoring applications where the objective
is to indicate the total energy in the system (that is, the
overall value), Calculated is the preferable measurement.
Calculated The RMS value of the time waveform multiplied by the square root of
two (1.414) if measuring the peak value, or two times the square root of
two (2.828) if measuring the peak-to-peak value.
IMPORTANT: When full scale is set to an RMS value, including
Calculated Peak or Calculated Peak-to-Peak, the XM module is
configured to accept input signals as high as 6X the specified full scale
without saturating the electronics. This is because a signal with
moderate RMS value may have very high spikes because RMS is an
averaging mechanism. If True Peak or True Peak-to-Peak is selected, the
module is configured to spread the full scale range over the entire
measurement range, without reserving this 6X headroom used for RMS.
This gives better resolution within the full scale range but causes the
signals to be clipped at levels just above the full scale.
High Pass Filter Corner Choose the high pass filter to apply to the measurement.
• 0.2 Hz
• 1 Hz
• 5 Hz
• 10 Hz
• 40 Hz The high pass filter is useful in removing low frequency signal
components that can dominate the signal, particularly when
integrating. The high pass filter attenuates frequencies less
than the specified frequency. It passes frequencies greater
than the specified frequency.
Enable Low Pass (Overall) Filter Check to apply a low pass filter to the Overall Measurement. Clear to
disable the low pass filter. The filter is applied only to the Overall measurement. It does
not affect the time waveform, spectrum, or measurements
derived from the spectrum.
Low Pass Filter Corner Enter a value between 100…20,000 Hz. Input signal frequencies
greater than this value are significantly attenuated. This parameter is available only when Enable Low Pass Filter
is checked.
When integrating, this (digital) Overall Low Pass Filter Corner
may not be set greater than the 2 kHz analog LPF that is
applied to all integrating measurements.
In this field Values are Comments