Spectral lines Vertical lines that make up a discrete spectrum. The height of a spectral line represents the amplitude of vibration at the frequency indicated by the spectral line. The more spectral lines used for a spectrum, the better the resolution of the spectrum (but the more instrument memory used and the longer the sampling duration required). See also Resolution and Spectrum.
Spectral map See Waterfall chart.
Spectral peak See Peak (w.r.t. spectrum).
Spectrum An amplitude (e.g. of velocity) versus frequency graph e.g. of measured vibration. A discrete vibration spectrum consists of a series of “spectral lines”, the height of each spectral line representing the amplitude at the frequency indicated by the spectral line. See also Waveform.
Spectrum analyzer An instrument capable of calculating a spectrum from a waveform. See also Fast Fourier transform.
Spring constant The ratio of applied force to the amount of distortion e.g. a spring that is compressed by 0.2 inch by a 2 lb force has a spring constant of 10 lbf/in. “k” is the symbol for spring constant. See also Stiffness.
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Beginner’s Guide To Machine Vibration