Watlow CLS200 - Manual (Page 230)

Glossary CLS200 Series User’s Guide
214 Watlow Anafaze Doc.# 0600-3050-2000
C
Calibration
The comparison of a measuring device (an
unknown) against an equal or better standard.
Celsius (Centigrade)
Formerly known as Centigrade. A temperature
scale in which water freezes at 0˚C and boils at
100˚C
at standard atmospheric pressure. The
formula for conversion to the Fahrenheit scale:
˚F = (1.8 x ˚C) + 32.
Central Processing Unit (CPU)
The unit of a computing system that includes
the circuits controlling the interpretation of
instructions and their execution.
Circuit
Any closed path for electrical current. A config-
uration of electrically or electromagnetically-
connected 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 met-
als 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 error between the process variable and
the setpoint. For reverse action (usually heat-
ing), as the process decreases below the set-
point the output increases. For direct action
(usually cooling), as the process increases
above the setpoint, the output increases.
Control Status
The type of action that a controller uses. For
example, on/off, time proportioning, PID, auto-
matic or manual, and combinations of these.
Current
The rate of flow of electricity. The unit of mea-
sure 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.
It provides a high level of data security but is
more difficult to implement than Block Check
Character (BCC). See also Block Check Char-
acter.
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.
Deadband
The range through which a variation of the
input produces no noticeable change in the
output. In the deadband, specific conditions
can be placed on control output actions. Opera-
tors select the deadband. It is usually above
the heating proportional band and below the
cooling proportional band.
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 anticipated the rate of change of the pro-
cess, and compensates to minimize overshoot
and undershoot. Derivative control is an
instantaneous change of the control output in
the same direction as the proportional error.
This is caused by a change in the process vari-
able (PV) that decreases over the time of the
derivative (TD). The TD is in units of seconds.
Deutsche Industrial Norms (DIN)