Rockwell Automation Publication ICSTT-RM447M-EN-P - July 2019 153
Glossary
Glossary of Terms
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
.
A
accuracy The amount of closeness of a measurement of a quantity to the true value of the
quantity. See also 'resolution'.
achievable safe state A safe state that is achievable.
Sometimes, a safe state cannot be achieved. An example is a non-recoverable
fault such as a voting element with a shorted switch and no means to bypass the
effect of the short.
actuator A device causing an electrical, mechanical, or pneumatic action to occur in a
plant component. Examples are valves and pumps.
AITA Analogue input termination assembly.
alarms and events (AE) An OPC data type providing time-stamped alarm and event notifications.
allotted process safety time The part of the total process safety time allotted to a sub function of a process.
application software Software written specially for a user application, typically using logic
sequences, limits and expressions to read inputs, make decisions and control
outputs for a specified system.
architecture Organizational structure of a computing system describing the functional
relationship between board level, device level and system level components.
asynchronous A data communications term describing a serial transmission protocol. A start
signal is sent before each byte or character and a stop signal is sent after each
byte or character. An example is ASCII over RS-232-C. See also 'RS-232-C,
RS-422, RS-485'.
availability The probability that a system can do its specified functions when required for
use. Normally expressed as a percentage.
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