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instrument transformer • Integrated Services Digital Network 371
instrument shunt
For ammeters, it is called a current transformer;
for voltmeters, it is called a potential transformer.
insulant A nonconducting material, used to prevent
the flow of electric current between or among
points. See INSULATOR, 1.
insulated Isolated from conductors by an INSU-
LANT.
insulated-gate field-effect transistor Abbreviation,
IGFET. See METAL-OXIDE SILICON FET.
insulated resistor A resistor around which is
molded a nonconducting material, such as vitreous
enamel or a plastic.
insulating tape Electrical insulation in the form of
a thin, usually adhesive, strip of fabric, paper, or
plastic.
insulation 1. A coating of dielectric material that
prevents a short circuit between a conductor and
the surrounding environment. 2. The application
of a dielectric coating to an electrical conductor.
3. Electrical separation between or among different
components, circuits, or systems.
insulation breakdown Current leakage through,
and rupture of, an insulating material because of
high-voltage stress.
insulation ratings Collectively, the dielectric constant,
dielectric strength, power factor, and resistivity
of an insulating material. Sometimes included
are such physical properties as rupture
strength, melting point, etc.
insulation resistance The very high resistance exhibited
by a good insulating material. It is expressed
in megohms (or higher units of resistance)
for a sample of material of stated volume or area.
insulation system Collectively, the materials
needed to insulate a given electronic device.
insulator 1. A material that, ideally, conducts no
electricity; it can, therefore, be used for isolation
and protection of energized circuits and components
(also see DIELECTRIC). Actually, no insulator
is perfectly nonconductive (see, for example,
INSULATION RESISTANCE). 2. A molded piece of
solid insulating material, used to electrically isolate
conductors—especially in antenna systems
and power transmission lines. 3. Any body made
from an insulating material.
insulator arcover A sudden arc, or flow of current,
over the surface of an insulator, because of excessive
voltage.
integer A positive or negative whole number, as
opposed to a fraction or mixed number.
integral 1. Also called indefinite integral and antiderivative.
For given mathematical function f,
function g, whose derivative is equal to f. 2. Also
called definite integral. The area under a curve of
a function, between two vertical lines defined by
two specific points in the domain of the function.
3. The part of a number to the left of the radix
point. 4. Pertaining to integers (positive or negative
whole numbers) or quantities that can be
represented by integers.
integral action In automatic control operations, a
control action delivering a corrective signal proportional
to the time that the controlled quantity
has differed from a desired value.
integral contact In a relay or switch, a contact
that carries current to be switched.
integral-horsepower motor A motor rated at one
horsepower.
integral multiple A whole multiple of a number.
Thus, a harmonic is an integral multiple of fundamental
frequency f: 2f, 3f, 4f, etc.
integral number See INTEGER.
integrate 1. To perform the function of mathematical
or electrical INTEGRATION. 2. To construct a
circuit on a piece of semiconductor material.
integrated Constructed on a single piece of material,
such as a semiconductor wafer.
integrated amplifier An audio-frequency (AF) amplifier
having a preamplifier, intermediate amplifier,
and output amplifier on a single chassis.
integrated capacitor In an integrated circuit, a
fixed capacitor in which one plate is a layer of material
diffused into the substrate, the dielectric is
a thin-oxide film grown on top of the first layer,
and the other plate is a metal layer deposited on
top of the oxide film.
integrated circuit Abbreviation, IC. A circuit
whose components and connecting “wires” are
made by processing distinct areas of a chip of
semiconductor material, such as silicon. Classified
according to construction (e.g., monolithic IC,
thin-film IC, hybrid IC).
integrated data processing Abbreviation, IDP.
The detailed electronic classification, sorting,
storage, and mathematical processing of data
within a coordinated system of equipment, usually
at one location.
integrated electronics The branch of electronics
that is concerned with the design and fabrication
of integrated circuits.
integrated resistor See DIFFUSED-LAYER RESIS-
TOR.
Integrated Services Digital Network Abbreviation,
ISDN. A communications network or connection
intended primarily for Internet access
via telephone lines. Allows significantly higher
data speed than is possible with a conventional
analog connection. In addition, it is possible to
use a digital system, such as a computer, online
simultaneously with an analog voice conversation.