Watlow CPC400 - Manual (Page 210)

Glossary CPC400 Series User’s Guide
196 Watlow Anafaze Doc. 0600-2900-2000
Circuit
Any closed path for electrical current. A configu-
ration of electrically or electromagnetically-con-
nected components or devices.
Closed Loop
A control system that uses a sensor to measure a
process variable and makes decisions based on
that feedback.
Cold Junction
Connection point between thermocouple metals
and the electronic instrument.
Common Mode Rejection Ratio
The ability of an instrument to reject electrical
noise, with relation to ground, from a common
voltage. Usually expressed in decibels (dB).
Communications
The use of digital computer messages to link
components. See also Serial Communications,
Baud Rate.
Control Action
The response of the PID control output relative to
the difference between the process variable and
the set point. See also Direct Action, Reverse
Action.
Current
The rate of flow of electricity. The unit of measure
is the Ampere (A). 1 Ampere = 1 coulomb per sec-
ond.
Cycle Time
The time required for a controller to complete one
on-off-on cycle. It is usually expressed in seconds.
Cyclic Redundancy Check (CRC)
An error checking method in communications
that provides a high level of data security.
D
DAC
See Digital-to-Analog Converter.
Data Logging
A method of recording a process variable over a
period of time. Used to review process perfor-
mance.
DC
See Direct Current.
Default Parameters
The programmed instructions that are perma-
nently stored in the microprocessor software.
Derivative Control (D)
The last term in the PID algorithm. Action that
anticipates the rate of change of the process and
compensates to minimize overshoot and under-
shoot. Derivative control is an instantaneous
change of the control output in the same direc-
tion as the proportional error. This is caused by a
change in the process variable that decreases
over the time of the derivative. The derivative is
expressed in seconds.
Deutsche Industrial Norms (DIN)
A set of technical, scientific and dimensional
standards developed in Germany. Many DIN
standards have worldwide recognition.
Deviation Alarm
See High Deviation Alarm, Low Deviation Alarm.
Digital-to-Analog Converter (DAC)
A device that converts a numerical input signal
to a signal that is proportional to the input in
some way.
DIN
See Deutsche Industrial Norms.
Direct Action
An output control action in which an increase in
the process variable causes an increase in the
output. Usually used with cooling applications.
Direct Current (DC)
An electric current that flows in one direction.
Distributed Zero Crossing (DZC)
A form of digital output control in which the out-
put on/off state is calculated for every ac line
cycle. Power is switched at the zero cross, which
reduces electrical noise. See also Zero Cross.
DZC
See Distributed Zero Crossing.
E
Earth Ground
A metal rod, usually copper, that provides an
electrical path to the earth, to prevent or reduce
the risk of electrical shock.
EIA/TIA
Electronic Industries Alliance (EIA) and Tele-
communications Industry Association (TIA). See
also Serial Communications.
EIA/TIA-232 — A standard for interface
between data terminal equipment and data
communications equipment for serial binary
data interchange. This is usually for communi-