Watlow Series D8 - Manual (Page 216)

Glossary Series D8 User’s Guide
198 Watlow Anafaze Doc. 0600-3120-2000
Celsius
A temperature scale in which w ater freezes at 0° C
and boils at 100° C at standard atmospheric pressure.
The formula for conversion to the F ahrenheit scale is
°F = (1.8 x °C) + 32. Formerly known as Centigrade.
Central Processing Unit (CPU)
The unit of a computing system that includes the cir -
cuits controlling the interpretation of instructions and
their execution.
Circuit
Any closed path for electrical current. A configuratio
of electrically or electromagnetically-connected com-
ponents or devices.
Class
The model for a software object. Objects of a class are
similar to one another. DeviceNet classes define wha
attributes and services objects of that type have. Class
services are used to e xamine and change class
attributes.
Closed Loop
A control system that uses a sensor to measure a pro-
cess variable and makes decisions based on that feed-
back.
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. Usu-
ally expressed in decibels (dB).
Communications
The use of digital computer messages to link compo-
nents. See also Serial Communications, Baud Rate.
Control Action
The response of the PID control output relati ve to the
difference between the process v ariable and the set
point. See also Direct Action, Reverse Action.
Current
The rate of fl w of electricity. The unit of measure is
the Ampere (A). 1 Ampere = 1 coulomb per second.
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 v ariable o ver a
period of time. Used to review process performance.
DC
See Direct Current.
Default Parameters
The programmed instructions that are permanently
stored in the microprocessor software.
Derivative Control (D)
The last term in the PID algorithm. Action that antici-
pates the rate of change of the process and compen-
sates to minimize o vershoot and undershoot.
Derivative control is an instantaneous change of the
control output in the same direction as the propor -
tional 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 stan
dards de veloped in German y. Man y DIN standards
have worldwide recognition.
Deviation Alarm
See High Deviation Alarm, Low Deviation Alarm.
DeviceNet
DeviceNet is a netw ork that connects industrial
devices. De viceNet is designed to pro vide a cost-
effective and rob ust solution to de vice netw orking.
DeviceNet is designed to transport control-oriented
information associated with lo w-level de vices and
other information related to the system being con-
trolled, such as configuration parameters
Digital-to-Analog Converter (DAC)
A device that con verts a numerical input signal to a
signal that is proportional to the input in some way.
DIN
See Deutsche Industrial Norms.