User`s manual

535 User's Manual Appendix 6 A-17
Glossary
APPENDIX 6
GLOSSARY
adaptive control: Control in which
automatic means are used to
change the type or influence (or
both) of control parameters in such
a way as to improve the
performance of the control system.
adaptive tune: A component of the
535 self tune function which
continuously monitors the process
and natural disturbances and makes
adjustments in the tuning
parameters to compensate for or
improve the performance of the
control system.
alarm: A condition, generated by a
controller, indicating that the process
has exceeded or fallen below the set
or limit point.
alarm, band: A type of alarm set up
where a band is created around the
control setpoint.
alarm, deviation: An alarm similar
to a band alarm except it only
creates a band on one side of the
alarm setpoint.
alarm, fault: An indication that
becomes active upon loss of
process variable. Fault alarm
operates in addition to other alarm
assignments.
alarm, global: The single physical
output to which one or more internal
software alarms are tied.
alarm, high process variable: A
type of alarm that is set up to occur
when the process variable goes
above the alarm setpoint.
alarm, low process variable: A
type of alarm that is set up to occur
when the process variable goes
below the alarm setpoint.
alarm, manual: A type of alarm set
up to occur when the controller is
put into manual mode of operation.
alarm, power up: A type of alarm
that determines alarm condition on
power up of the controller.
alarm, rate-of-change: A type of
alarm set up to occur when there is
an excessive change in the process
variable (PV) value.
baud rate: Any of the standard
transmission rates for sending or
receiving binary coded data.
bezel: The flat portion surrounding
the face of the controller, which
holds the keys and display.
bump: A sudden increase in the
output power initiated by the
controller in order to determine the
system response during a self tune
procedure.
binary coded decimal (BCD): A
notation in which the individual
decimal digits are represented by a
group of binary bits, e.g., in the 8-4-
2-1 coded decimal notation each
decimal digit is represented by four
binary bits.
calibration: The act of adjustment
or verification of the controller unit by
comparison of the unit’s reading and
standards of known accuracy and
stability.
cascade control: Control in which
the output of one controller is the
setpoint for another controller.
closed loop: Control system that
has a sensing device for process
variable feedback.
cold junction: Point of connection
between thermocouple metals and
the electronic instrument.
configuration: Also called “set up,”
selection of hardware devices and
software routines that function
together.
cold junction compensation:
Electronic means used to
compensate for the effect of
temperature at the cold junction.
contact: In hardware, a set of
conductors that can be brought into
contact by electromechanical action
and thereby produce switching. In
software, a symbolic set of points
whose open or closed condition
depends on the logic status
assigned to them by internal or
external conditions.
control action: The slope of the
output of the instrument in reference
to the input, e.g., direct output
increases on rise of input. Typical
cooling response or reverse output
decreases on rise of input (typical
heating response).
control action, derivative (rate)
(D): The part of the control algorithm
that reacts to rate of change of the
process variable.
control action, integral (reset) (I):
The part of the control algorithm that
reacts to offset between setpoint
and process variable.
control action, proportional (P):
Control action in which there is a
continuous linear relation between
the output and the input.
control action, proportional plus
derivative (PD): A control algorithm
that provides proportional control
with the addition of derivative action
to compensate for rapid changes in
process variable.