Neper

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Neper

For Neper as a mythological god, see Neper (mythology)
Neper (mythology)

In Egyptian mythology, Neper was an Androgyny deification of cereal, a valuable commodity in ancient Egypt, which faced starvation without it....
, for the lunar crater named Neper, see Neper (crater)
Neper (crater)

Neper is an old moon impact crater located near the eastern limb of the Moon. Due to its location the crater must be viewed during a suitable libration, and is very foreshortened....
, and for the Scottish mathematician, phycisist and astronomer, see John Napier
John Napier

John Napier of Merchistoun - also signed as Neper, Nepair - named Marvellous Merchiston, was a Scotland mathematics, physicist, astronomer/astrologer and 8th Laird of Merchistoun, son of Sir Archibald Napier of Merchiston....
.

A neper (Symbol: Np) is a logarithmic unit of ratio

Ratio

A ratio is an expression which compares quantities relative to each other. The most common examples involve two quantities, but in theory any number of quantities can be compared....
. It is not an SI

Si, si, or SI may refer to :...
unit but is accepted for use alongside the SI. It is used to express ratios, such as gain

Gain

In electronics, gain is a measure of the ability of a electrical network to increase the Power or amplitude of a Signal . It is usually defined as the mean ratio of the Signalling of a system to the Signalling of the same system....
and loss, and relative values. The name is derived from John Napier

John Napier

John Napier of Merchistoun - also signed as Neper, Nepair - named Marvellous Merchiston, was a Scotland mathematics, physicist, astronomer/astrologer and 8th Laird of Merchistoun, son of Sir Archibald Napier of Merchiston....
, the inventor of logarithms.

Like the decibel

Decibel

The decibel is a logarithmic units of measurement that expresses the magnitude of a physical quantity relative to a specified or implied reference level....
, it is a unit in a logarithmic scale

Logarithmic scale

A logarithmic scale is a scale that uses the logarithm of a physical quantity instead of the quantity itself.Presentation of data on a logarithmic scale can be helpful when the data covers a large range of values – the logarithm reduces this to a more manageable range....
, the difference being that where the decibel uses base-10 logarithm

Logarithm

In mathematics, the logarithm of a number to a given base is the Power or exponent to which the base must be raised in order to produce the number....
s to compute ratios, the neper uses base e

E (mathematical constant)

The mathematical constant e is the unique real number such that the function ex has the same value as the derivative, for all values of x....
˜ 2.71828.

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Encyclopedia

A neper (Symbol: Np) is a logarithmic unit of ratio

Ratio

Si, si, or SI may refer to :...
unit but is accepted for use alongside the SI. It is used to express ratios, such as gain

Gain

John Napier

Decibel

Logarithmic scale

Logarithm

In mathematics, the logarithm of a number to a given base is the Power or exponent to which the base must be raised in order to produce the number....
s to compute ratios, the neper uses base e

E (mathematical constant)

The mathematical constant e is the unique real number such that the function ex has the same value as the derivative, for all values of x....
˜ 2.71828. The value of a ratio in nepers, Np, is given by

where and are the values of interest, and ln is the natural logarithm

Natural logarithm

The natural logarithm, formerly known as the hyperbolic logarithm, is the logarithm to the base e , where e is an irrational number constant approximately equal to 2.718281828....
.

The neper is often used to express ratios of voltage

Voltage

Electrical tension is the potential difference between two points of an electrical or electronic circuit, expressed in volts. It is the measurement of the potential for an electric field to cause an electric current in an electrical conductor....
and current amplitudes in electrical circuits (or pressure

Sound pressure

Sound pressure is the local pressure deviation from the ambient pressure caused by a sound wave. Sound pressure can be measured using a microphone in air and a hydrophone in water....
in acoustics

Acoustics

Acoustics is the interdisciplinary science that deals with the study of sound, ultrasound and infrasound . A scientist who works in the field of acoustics is an acoustician....
), whereas the decibel

Decibel

The decibel is a logarithmic units of measurement that expresses the magnitude of a physical quantity relative to a specified or implied reference level....
is used to express power

Power (physics)

In physics, power is the rate at which mechanical work is performed or energy is transmitted, or the amount of energy required or expended for a given unit of time....
ratios. One kind of ratio may be converted into the other. Considering that wave power is proportional to the square of the amplitude, we have

and

The decibel and the neper have a fixed ratio to each other. The (voltage) level is

Like the decibel, the neper is a dimensionless unit. The ITU

International Telecommunication Union

The International Telecommunication Union is the second-oldest international organization still in existence , established to standardize and regulate international radio and telecommunications....
recognizes both units.

External links

Sources

Federal Standard 1037C
Federal Standard 1037C

Federal Standard 1037C, entitled Telecommunications: Glossary of Telecommunication Terms is a United States Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended....
MIL-STD-188
MIL-STD-188

MIL-STD-188 is a series of U.S. military standards relating to telecommunications....