A nominally continuous electrical signal that varies in amplitude or frequency in response to changes in sound, light, heat, position, or pressure.


Related Terms

MODULUS OF DECAY

The time required for the amplitude of oscillation of an underdamped harmonic oscillator to drop to 1/e of its initial value; the reciprocal of the damping factor.

MECHANOOPTICAL VIBROMETER

A vibrometer in which the motion given to a probe by a surface whose vibration amplitude is to be measured is used to rock a mirror; a light beam reflected from the mirror and focused onto a scale provides an indication of the vibration amplitude.

MAGNETO ANEMOMETER

A cup anemometer with its shaft mechanically coupled to a magnet; both the frequency and amplitude of the voltage generated are proportional to the wind speed, and may be indicated or recorded by suitable electrical instruments.

LIMITER

An electronic circuit used to prevent the amplitude of an electronic waveform from exceeding a specified level while preserving the shape of the waveform at amplitudes less than the specified level. Also known as amplitude limiter; amplitude-limiting circuit; automatic peak limiter; clipper; clipping circuit; limiter circuit; peak limiter.

JUMP PHENOMENON

A phenomenon occurring in a nonlinear system subjected to a sinusoidal input at constant frequency, in which the value of the amplitude of the forced oscillation can jump upward or downward as the input amplitude is varied through either of two fixed values, and the graph of the forced amplitude versus the input amplitude follows a hysteresis loop.

IMPULSE MODULATION

Modulation of a signal in which it is replaced by a series of impulses, equally spaced in time, whose strengths (integrals over time) are proportional to the amplitude of the signal at the time of the impulse.

FRETTING

Wear phenomena taking place between two surfaces having oscillatory relative motion of small amplitude.

INTERFERENCE

1. Unwanted and confusing signals or patterns produced by nearby electrical equipment or machinery, or by atmospheric phenomena. 2. The variation of wave amplitude with distance or time, caused by superposition of two or more waves. Sometimes called WAVE INTERFERENCE.

ALMUCANTAR STAFF

An ancient instrument formerly used for amplitude observations

AMPLITUDE MODULATION

The process of changing the amplitude of a carrier wave in accordance with the variations of a modulating wave. See also MODULATION.

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