Neper. Relative unit of measurement frequently used in the field of telecommunications , through which relationships between voltages or currents can be expressed . Its symbol is Np.


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  • 1 Origin
  • 2 Definition
  • 3 Equivalence with the unity of the International System
  • 4 Note on terminology
  • 5 See also
  • 6 Reference
  • 7 Source


The neper, also known as the neper, owes its name to John Napier , born in Edinburgh , Scotland , in 1550 , who died in the same city in the year 1617 , went down in history as a famous mathematician for the invention of logarithms and of various contributions to different branches of mathematics : geometry , trigonometry , algebra and what at that time were called commercial mathematics. He invented what is known as Napier strips which was an instrument to multiply that later became popular and that several men of the RenaissanceThey used, throughout Europe , as a very useful calculation tool.


Neper 1 : Unit used to express the ratio of two powers , equivalent to 0.868 6 bel (1 bel equals 1,151 neperes).

  • The neper allows evaluating the ratio of two voltagesor two electronic powers , of two pressures , etc., according to the formula:

N (in neper) = log p1 / p2

In which p1 and p2 are the two pressures or other considerable magnitudes.

The neper is mainly used to evaluate acoustic intensities and the attenuation and amplification of telephone currents. Although the neper is not a unit of measurement of the International System , its use is widely accepted in many countries, for the same purposes as the decibel . The fundamental difference between the two units is that while the decibel is based on the logarithm decimal relationship of magnitudes, the neper what is the logarithm natural and neperiano of said ratio.

Equivalence with the unity of the International System

In the International System the unit of measurement is the decibel , it is the tenth of 1 bel; The following table shows an equivalence relationship between both units:

Neper (Np) Decibel (dB)
8.68 Np 1 dB
477.72 Np 55 dB
521.15 Np 60 dB

Terminology Note

This unit of the International System of Units is named after John Napier . In units of measurement whose name comes from a person’s own name, the first letter of the symbol is capitalized (Np), while its name always begins with a lowercase letter (neper), except when it starts a phrase or a title.


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