Immittance
Encyclopedia
Immittance in electrical and acoustical terminology is a concept combining the impedance
and admittance
of a system or circuit. The term was invented by Bode
.
It is sometimes convenient to use the term immittance when referring to a complex number
which may be either the impedance (ratio of volt
age to current
in electrical circuits, or sound pressure
to volume velocity in acoustical systems) or the admittance (ratio of current to voltage, or volume velocity to sound pressure) of a system. In audiology
, tympanometry
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
simply has both the impedance and admittance grids on the same chart, which is useful for cascading series-connected with parallel-connected circuits.
Electrical impedance
Electrical impedance, or simply impedance, is the measure of the opposition that an electrical circuit presents to the passage of a current when a voltage is applied. In quantitative terms, it is the complex ratio of the voltage to the current in an alternating current circuit...
and admittance
Admittance
In electrical engineering, the admittance is a measure of how easily a circuit or device will allow a current to flow. It is defined as the inverse of the impedance . The SI unit of admittance is the siemens...
of a system or circuit. The term was invented by Bode
Hendrik Wade Bode
Hendrik Wade Bode , was an American engineer, researcher, inventor, author and scientist], of Dutch ancestry. As a pioneer of modern control theory and electronic telecommunications he revolutionized both the content and methodology of his chosen fields of research.He made important contributions...
.
It is sometimes convenient to use the term immittance when referring to a complex number
Complex number
A complex number is a number consisting of a real part and an imaginary part. Complex numbers extend the idea of the one-dimensional number line to the two-dimensional complex plane by using the number line for the real part and adding a vertical axis to plot the imaginary part...
which may be either the impedance (ratio of volt
Volt
The volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...
age to current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
in electrical circuits, or sound pressure
Sound pressure
Sound pressure or acoustic pressure is the local pressure deviation from the ambient atmospheric pressure caused by a sound wave. Sound pressure can be measured using a microphone in air and a hydrophone in water...
to volume velocity in acoustical systems) or the admittance (ratio of current to voltage, or volume velocity to sound pressure) of a system. In audiology
Audiology
Audiology is the branch of science that studies hearing, balance, and related disorders. Its practitioners, who treat those with hearing loss and proactively prevent related damage are audiologists. Employing various testing strategies Audiology (from Latin , "to hear"; and from Greek , -logia) is...
, tympanometry
Tympanometry
Tympanometry is an examination used to test the condition of the middle ear and mobility of the eardrum and the conduction bones by creating variations of air pressure in the ear canal....
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
Smith chart
The Smith chart, invented by Phillip H. Smith , is a graphical aid or nomogram designed for electrical and electronics engineers specializing in radio frequency engineering to assist in solving problems with transmission lines and matching circuits...
simply has both the impedance and admittance grids on the same chart, which is useful for cascading series-connected with parallel-connected circuits.