Dictionary:

amplitude

  (ăm'plĭ-tūd', -tyūd')

1. Greatness of size; magnitude.
2. Fullness; copiousness.
3. Breadth or range, as of intelligence.
4. Astronomy. The angular distance along the horizon from true east or west to the intersection of the vertical circle of a celestial body with the horizon.
5. Physics. The maximum absolute value of a periodically varying quantity.
6. Mathematics.
   1. The maximum absolute value of a periodic curve measured along its vertical axis.
   2. The angle made with the positive horizontal axis by the vector representation of a complex number.
7. Electronics. The maximum absolute value reached by a voltage or current waveform.

[Latin amplitūdō, from amplus, large.]

The maximum magnitude (value without regard to sign) of the disturbance of a wave. The term “disturbance” refers to that property of a wave which perturbs or alters its surroundings. It may mean, for example, the displacement of mechanical waves, the pressure variations of a sound wave, or the electric or magnetic field of light waves. Sometimes in older texts the word amplitude is used for the disturbance itself; in that case, amplitude as meant there is called peak amplitude. This is no longer common usage.

If the medium which a wave disturbs dissipates the wave by some nonlinear behavior or other means, then the amplitude will, in general, depend upon position. See also Light; Sound; Wave motion.

The strength or volume of a signal, usually measured in decibels. See wavelength.

Amplitude

The amplitude is the power of a signal. The greater the amplitude, the greater the energy carried.

noun

1. Great extent, amount, or dimension: bulk, magnitude, mass, size, volume (often used in plural). See big/small/amount.
2. The quality or state of being large in amount, extent, or importance: bigness, greatness, largeness, magnitude, sizableness, size. See big/small/amount.

Of oscillation or vibration, the maximum displacement from the mean position.

In physics, the height of a crest (or the depth of a trough) of a wave.

Largeness, fullness; wideness or breadth of range or extent.

• a. mode — see A-mode ultrasonography.

Magnitude or size of a signal voltage or current.

For quantum-mechanical amplitude, see probability amplitude. For the video game of the same name, see Amplitude (video game).

The amplitude is a nonnegative scalar measure of a wave's magnitude of oscillation, that is, the magnitude of the maximum disturbance in the medium during one wave cycle.

The displacement y is the amplitude of the wave

Sometimes this distance is called the peak amplitude, distinguishing it from another concept of amplitude, used especially in electrical engineering: the RMS or root mean square amplitude, defined as the square root of the temporal mean of the square of the vertical distance of this graph from the horizontal axis. The use of peak amplitude is unambiguous for symmetric, periodic waves, like a sine wave, a square wave, or a triangular wave. For an asymmetric wave (periodic pulses in one direction, for example), the peak amplitude becomes ambiguous because the value obtained is different depending on whether the maximum positive signal is measured relative to the mean, the maximum negative signal is measured relative to the mean, or the maximum positive signal is measured relative the maximum negative signal (the peak-to-peak amplitude) and then divided by two.

Different amplitude measurements of a sine wave

For complex waveforms, especially non-repeating signals like noise, the RMS amplitude is usually used because it is unambiguous and because it has physical significance. For example, the average power transmitted by an acoustic or electromagnetic wave or by an electrical signal is proportional to the square of the RMS amplitude (and not, in general, to the square of the peak amplitude).

There are a few ways to formalize amplitude:

In the simple wave equation

A is the amplitude of the wave.

The units of the amplitude depend on the type of wave.

For waves on a string, or in medium such as water, the amplitude is a displacement.

The amplitude of sound waves and audio signals (also referred to as Volume) conventionally refers to the amplitude of the air pressure in the wave, but sometimes the amplitude of the displacement (movements of the air or the diaphragm of a speaker) is described. The logarithm of the amplitude squared is usually quoted in dB, so a null amplitude corresponds to -∞ dB. Loudness is related to amplitude and intensity and is one of most salient qualities of a sound, although in general sounds can be recognized independently of amplitude.

For electromagnetic radiation, the amplitude corresponds to the electric field of the wave. The square of the amplitude is proportional to the intensity of the wave.

The amplitude may be constant (in which case the wave is a continuous wave) or may vary with time and/or position. The form of the variation of amplitude is called the envelope of the wave.

Pulse amplitude

In telecommunication, pulse amplitude is the magnitude of a pulse parameter, such as the field intensity, voltage level, current level, or power level.

Note 1: Pulse amplitude is measured with respect to a specified reference and therefore should be modified by qualifiers, such as "average", "instantaneous", "peak", or "root-mean-square."

Note 2: Pulse amplitude also applies to the amplitude of frequency- and phase-modulated waveform envelopes.

Source: from Federal Standard 1037C

See also

• Waves and their properties:
  • Frequency
  • Period
  • Wavelength
  • Crest factor
• Amplitude modulation

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
n. - vidde, udstrækning

Nederlands (Dutch)
amplitude, uitgestrektheid, overvloed

Français (French)
n. - (Astron, Phys) amplitude, ampleur (d'une pensée)

Deutsch (German)
n. - (electr.) Amplitude, Schwingungsweite

Ελληνική (Greek)
n. - εύρος, πλάτος, ευρύτητα, αφθονία

Italiano (Italian)
ampiezza, abbondanza

Português (Portuguese)
n. - amplitude (f), extensão (f), abundância (f), plenitude (f)

Русский (Russian)
амплитуда

Español (Spanish)
n. - amplitud, extensión, abundancia

Svenska (Swedish)
n. - vidd, bredd, amplitud

中文（简体） (Chinese (Simplified))
广阔, 广大, 振幅, 丰富, 充足, 射程

中文（繁體） (Chinese (Traditional))
n. - 廣闊, 廣大, 振幅, 豐富, 充足, 射程

한국어 (Korean)
n. - 넓이, 풍부

日本語 (Japanese)
n. - 広さ, 豊富, 振幅

العربيه (Arabic)
‏(الاسم) اتساع, وفره, مدى, نطاق‏

עברית (Hebrew)
n. - ‮גודל, משרעת, שפע, שפעה‬

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