Measurement Computing eZ-Analyst rev.14.1 - Manual (Page 131)

eZ-Analyst 959294 Glossary G-1
Glossary
Accelerometer
A type of transducer that produces an output voltage proportional to acceleration.
Acquisition
A collection of scans acquired at a specified rate as controlled by the sequencer.
Analog Signal
A signal of varying voltage or current, resistance, temperature such as the output of a sensor.
Many analog signals are in the form of sine waves.
Apparent Mass
Force/Acceleration. A transfer type that is the reciprocal function of Inertance. Apparent
Mass is derived by taking the inverse of the magnitude, and multiplying the phase angle by “-
1.”
Auto-Spectrum Function
A single-channel display function. Displays the square of the magnitude of the complex (one-
side) Fourier spectrum of x(t). Autospectra are calibrated so that if A is the peak amplitude of
a sinusoidal signal x(t), then the autospectrum has the value A*A (or use A power 2) at the
sinusoidal frequency.
Averaged Time Function
A single-channel display function. Displays a time domain waveform of averaged, sampled
data scaled in either Volts or Engineering Units (EUs).
Bank
A set of response channels.
Blackman-Harris
An FFT window function. This window function was designed to provide the minimum side
lobe level of any three-term window. Compared with the very similar Hanning window, it has
a slightly wider main lobe but much better dynamic range. This window has the smallest 60
dB bandwidth of any window listed. The Blackman-Harris window may be preferred over the
Hanning for measurements requiring better dynamic range.
Channel
A single input, or output for the acquisition device. In a broader sense, an input channel is a
signal path between the transducer at the point of measurement and the data acquisition
system. A channel can go through various stages (buffers, multiplexers, or signal conditioning
amplifiers and filters). Input channels are periodically sampled for readings. An output
channel from a device can be digital or analog. Outputs can vary in a programmed way in
response to an input channel signal.
Coherence Function
A dual-channel display function. At each frequency, the coherence is a value between 0.0 and
1.0, which indicates the degree of consistent linear relationship between two signals during
the averaging process. A value of less than one indicates that phase cancellation occurred
during cross-spectrum averaging, which may be due to uncorrelated noise on one or both
signals or to a nonlinear relationship between signals.
Compliance, also referred to as Receptance
Displacement/Force. The transfer type function is calculated by dividing the cross spectrum of
the channel pair by the auto spectrum of the reference (force) channel.
CPM
Cycles per Minute. 60 CPM is equal to 1 Hz.