Instruction Manual

Rockwell Automation Publication 1769-UM006E-EN-P - July 2013 157
Glossary
The following terms and abbreviations are used throughout this manual. For
definitions of terms not listed here, refer to the Allen-Bradley Industrial
Automation Glossary, publication
AG-7.1.
accumulated value (ACC) The number of elapsed time intervals or counted events.
actuator 1) A device that converts an electrical signal into mechanical motion. 2) In a
general sense, any machine/process load device (for example, transducer) of a
controller output circuit. See output device (
page 162).
address 1) A character string that uniquely identifies a memory location. 2) A character
string that uniquely identifies the physical location of an input or output circuit.
algorithm A set of procedures used for solving a problem in a finite number of steps.
American wire gauge (AWG) A standard system used for designating the size of electrical conductors. Gauge
numbers have an inverse relationship to size; larger numbers have a smaller cross-
sectional area. However, a single-strand conductor has a larger cross-sectional area
than a multi-strand conductor of the same gauge so that they have the same
current-carrying specification.
analog circuit 1) A circuit in which the signal can vary continuously between specified limits. 2)
A circuit that provides a continuous function. 3) Contrasted with digital circuit
(
page 159).
asynchronous 1) Lacking a regular time relationship; not related through repeating time
patterns. 2) Contrasted with synchronous (
page 163).
AWG See American wire gauge (
page 157).
backplane A printed-circuit board, at the back of a chassis, that provides electrical
interconnection between the modules inserted into the chassis.
balanced circuit 1) A circuit whose two sides are electrically alike and symmetrical to a common
reference point, usually ground. 2) Contrasted with unbalanced circuit
(
page 163).
bandwidth The range of frequencies over which a system is designed to operate. The
bandwidth is expressed in Hertz between the highest and lowest frequencies.
baseband link 1) A communication link with only one channel, encoded by on/off switching.
Examples: DH and DH+ links. 2) Contrasted with carrier-band link
(
page 158) and broadband link (page 158).
bidirectional I/O module An I/O module whose communication with the scanner or processor is
bidirectional and therefore uses both input and output image areas.