In electrical engineering and acoustics, immittance is a concept combining the
impedance and
admittance of a system or circuit. The term ''immittance'' was invented by
H. W. Bode.
[
]
It is sometimes convenient to use ''immittance'' to refer to a
complex number
In mathematics, a complex number is an element of a number system that extends the real numbers with a specific element denoted , called the imaginary unit and satisfying the equation i^= -1; every complex number can be expressed in the fo ...
which may be either the impedance (ratio of
volt
The volt (symbol: V) is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827).
Defin ...
age to
current
Currents, Current or The Current may refer to:
Science and technology
* Current (fluid), the flow of a liquid or a gas
** Air current, a flow of air
** Ocean current, a current in the ocean
*** Rip current, a kind of water current
** Current (stre ...
in electrical circuits, or
sound pressure to
volume velocity
In physics and engineering, in particular fluid dynamics, the volumetric flow rate (also known as volume flow rate, or volume velocity) is the volume of fluid which passes per unit time; usually it is represented by the symbol (sometimes ). I ...
in acoustical systems) or the admittance (ratio of current to voltage, or volume velocity to sound pressure) of a system. In
audiology
Audiology (from Latin , "to hear"; and from Greek , ''-logia'') is a branch of science that studies hearing, balance, and related disorders. Audiologists treat those with hearing loss and proactively prevent related damage. By employing vario ...
,
tympanometry
Tympanometry is an acoustic evaluation of the condition of the middle ear eardrum (tympanic membrane) and the conduction bones by creating variations of air pressure in the ear canal.
Tympanometry is an objective test of middle-ear function. It is ...
is sometimes called ''immittance testing''.
Immittance does not have units since it applies to both impedance and admittance, which have different units. However, in certain theoretical work it may be necessary to deal with general functions, which afterward will be specialised to become either an impedance or an admittance by the assignment of suitable units; in such cases it is convenient to refer to the functions as immittances.
In electronics, the "immittance"
Smith chart
The Smith chart, invented by Phillip H. Smith (1905–1987) and independently by Mizuhashi Tosaku, is a graphical calculator or nomogram designed for electrical and electronics engineers specializing in radio frequency (RF) engineering to assis ...
simply has both the impedance and admittance grids on the same chart, which is useful for cascading series-connected with parallel-connected electric circuits.
References
{{Refimprove, date=April 2007
Physical quantities
Electrical parameters