Watlow CAS - Manual (Page 89)

CAS User’s Guide 79
Glossary
A
AC
See Alternating Current.
AC Line Frequency
The frequency of the AC power line measured in
Hertz (Hz), usually 50 or 60 Hz.
Accuracy
Closeness between the value indicated by a mea-
suring instrument and a physical constant or
known standards.
Action
The response of an output when the process vari-
able is changed. See also Direct action, Reverse
action.
Address
A numerical identifier for a controller when used
in computer communications.
Alarm
A signal that indicates that the process has
exceeded or fallen below a certain range around
the setpoint. For example, an alarm may indicate
that a process is too hot or too cold. See also:
Deviation Alarm
Failed Sensor Alarm
Global Alarm
High Deviation Alarm
High Process Alarm
Loop Alarm
Low Deviation Alarm
Low Process Alarm
Alarm Delay
The lag time before an alarm is activated.
Alternating Current (AC)
An electric current that reverses at regular inter-
vals, and alternates positive and negative values.
Ambient Temperature
The temperature of the air or other medium that
surrounds the components of a thermal system.
American Wire Gauge (AWG)
A standard of the dimensional characteristics of
wire used to conduct electrical current or signals.
AWG is identical to the Brown and Sharpe
(B&S) wire gauge.
Ammeter
An instrument that measures the magnitude of an
electric current.
Ampere (Amp)
A unit that defines the rate of flow of electricity
(current) in the circuit. Units are one coulomb
(6.25 x 1018 electrons) per second.
Analog Output
A continuously variable signal that is used to rep-
resent a value, such as the process value or set-
point value. Typical hardware configurations are
0-20mA, 4-20mA or 0-5 Vdc.
Automatic Mode
A feature that allows the controller to set PID
control outputs in response to the Process Vari-
able (PV) and the setpoint.
Autotune
A feature that automatically sets temperature
control PID values to match a particular thermal
system.
B
Bandwidth
A symmetrical region above and below the set-
point in which proportional control occurs.
Baud Rate
The rate of information transfer in serial commu-
nications, measured in bits per second.