Watlow CLS200 - Page 172

CLS200 Series User’s Guide
172
Autotune
A feature that automatically sets temperature
control PID values to match a particular thermal
system.
AWG
See American Wire Gauge.
B
Baud Rate
The rate of information transfer in serial
communications, measured in bits per second.
Block Check Character (BCC)
A serial communications error checking method.
See also Cyclic Redundancy Check.
Bumpless Transfer
A smooth transition from automatic (closed
loop) to manual (open loop) operation. The
control output does not change during the
transfer.
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 configuration 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 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 error between the process variable and
the setpoint. For reverse action (usually heating),
as the process decreases below the setpoint
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,
automatic or manual, and combinations of
these.
Current
The rate of flow 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.
It provides a high level of data security but is
more difficult to implement than Block Check
Character (BCC). See also Block Check
Character.