Condition Monitoring Systems


Warm Up Period

he time required after energizing a device before its rated performance characteristics start to apply.

Waterfall plot

A series of spectral maps taken at regular intervals of time, regularly spaced shaft speeds, etc. Early maps move down the display, followed by later maps, something like the flow of a waterfall.


Nature’s mechanism for transporting energy without transporting matter.


A presentation or display of the instantaneous amplitude of a signal as a function of time, as on an oscilloscope or oscillograph. In the time domain.


As used for shock testing on shakers, are half-sine windowed (amplitude modulated) sinusoids of specific frequencies, with the window chosen so the resulting waveforms have an odd number of half cycles. Usually, ten to thirty wavelets, each with different basis frequencies, e.g., 10 Hz to 2000 Hz, and different numbers of half cycles, e.g., three to 31 or so, are superimposed to synthesize a transient oscillatory signal (pulse) with a prescribed Shock Response Spectrum that can be used as a reference waveform for a shaker shock test.


That property of an object that can be weighed, as on a scale; the gravitational force on an object.

Weighting (Acoustic)

Emphasis or attenuation applied to sound measurements at certain frequencies. C weighting is essentially flat. A weighting attempts to compensate for the non-constant sensitivity of human hearing at certain frequencies.

White random vibration

That broad-band random vibration in which the power spectral density (PSD (ASD) is constant over a broad frequency range.


A “weighting function” applied to time-data prior to performing an FFT. Rectangular, Hann, Flat top, DP7, BH4, Force and Response.


Rotation about the vertical axis.

Zwicker loudness

A sound measurement methodology. Loudness is measured in linear units called sones as opposed to decibels.

Zero-G drift

The amount that a sensor’s signal shifts over some temperature range.

Zero-G output

The output that is read when the sensor is not accelerating.


See peak, as in peak value. Half of the peak-to-peak value.