D8 Series User’s Guide
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AWG
See American Wire Gauge.
B
Baud Rate
The rate of information transfer in serial
communications, measured in bits per second.
BCD
Binary coded decimal. For BCD job loading, the
binary states of three digital inputs are decoded
as decimal numbers 1 to 8.
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
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 is °F = (1.8 x °C) + 32.
Formerly known as Centigrade.
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 electromagnet-
ically-connected components or devices
Class
The model for a software object. Objects of a
class are similar to one another. DeviceNet™
classes define what attributes and services
objects of that type have. Class services are
used to examine and change class attributes.
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 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 variable
over a period of time. Used to review process
performance.
DC
See Direct Current.
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