||The smallest interval of time in which a cyclic vibration repeats itself.
|Periodic vibration (same as deterministic vibration)
||An oscillation whose waveform regularly repeats. Compare with probabilistic vibration.
||(Of periodic quantity), the fractional part of a period between a reference time (such as when x=0) and a particular time of interest or between two
motions of electrical signals having the same fundamental frequency.
||One which depends upon deformation of its sensitive crystal or ceramic element to generate electrical charge and voltage. Many present day accelerometers
||Per MIL-STD-810D, any vehicle, surface or medium that carries an equipment. For example, an aircraft is the carrying platform for internally installed
avionics equipment and externally mounted stores.
|Power spectral density or PSD
||Describes the power of random vibration intensity, in mean-square x per frequency units, as g2/Hz or m2/s3. Accelerated spectral density or ASD is
||One whose magnitude at any future time can only be predicted on a statistical basis.
||(or side or lateral motion or cross tald) any motion perpendicular to the reference axis. Shakers are supposed to have zero quadrature motion.
|Random vibration (same as probablistic vibration)
||One whose instantaneous magnitudes cannot be predicted. Adjective Gaussian applies if they follow the Gaussian distribution. May be broad band,
covering a wide continuous frequency range, or narrow band covering a relatively narrow frequency range. No periodic or deterministic components.
||Redundancy, wherein all redundant items are operating simultaneously rather than being switched on when needed.
||Redundancy, wherein the alternative means of performing the function is inoperative until needed and is switched on upon failure of the primary means of
performing the function.
||1. The ability of an item to perform a required function under stated conditions for a stated period of time. 2. The characteristic of an item expressed
by the probability that it will perform a required function under stated conditions for a stated period of time. Definition (2) is most commonly used in
||1. The maximum deviation from the mean of corresponding data points taken under identical conditions. 2. the maximum difference in output for identically
repeated stimuli (no change in other test condition).
||The smallest change in input that will produce a detectable change in an instrumentís output. Differs from precision in that human capabilities are
||Forced vibration of a true SD of system causes resonance when f=fn, when any freq change decreases system response. Therefore, resonance represents
maximum sprung mass response, if freq. is varied while input F is held constant.
||Continued oscillation after an external force or excitation is removed, as after a guitar string is plucked.
||A test or combination of tests intended to remove unsatisfactory items or those likely to exhibit early failures
||Of a mechanical to electrical sensor or pickup, the ratio between electrical signal (output) and mechanical quantity (input).
||Or shock test machine, a device for subjecting a system to controlled and reproducible mechanical shock pulses.