535-PROF 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.
control action, proportional plus
integral (PI):
A control algorithm that
provides proportional control with the
addition of integral action to
compensate for offsets between
setpoint and process variable.
control action, proportional plus
integral plus derivative (PID):
A
control algorithm that provides
proportional control with both integral
and derivative action.
control, adaptive:
(see adaptive
control)
control algorithm:
A mathematical
representation of the control action to
be performed.
control, cascade:
(see cascade
control)
