Rockwell Automation 1746-NI16V SLC 500 Analog Input Modules User Manual - Manual (Page 111)

1 Publication 1746-UM001A-US-P
Glossary
The following terms and abbreviations are used throughout this
manual. For definitions of terms not listed here refer to Allen-Bradley’s
Industrial Automation Glossary, Publication AG-7.1.
A/D - Refers to the analog to digital converter inherent to the module.
The converter produces a digital value whose magnitude is
proportional to the instantaneous magnitude of an analog input signal.
analog input module - An I/O module that contains circuits that
convert analog dc input signals to digital values that can be
manipulated by the processor.
attenuation - The reduction in the magnitude of a signal as it passes
through a system.
backplane -A printed circuit board, at the back of the chassis, that
provides electrical interconnection between the modules inserted into
the chassis.
channel - Refers to one of eight, small-signal analog input interfaces
available on the module’s terminal block. Each channel is configured
for connection to a voltage or current source input device and has its
own data and diagnostic status words.
channel update time - The time required for the module to sample
and convert the input signals of one enabled input channel and
update the channel data word.
chassis - A hardware assembly that houses devices such as I/O
modules, adapter modules, processor modules, and power supplies.
common mode rejection ratio - The ratio of a device’s differential
voltage gain to common mode voltage gain. Expressed in dB, CMRR is
a comparative measure of a device’s ability to reject interference
caused by a voltage common to its input terminals relative to ground.
CMRR=20 Log
10 (V1/V2)
common mode voltage - A voltage that appears in common at both
input terminals of a differential analog input with respect to ground.
configuration word - Contains the channel configuration
information needed by the module to configure and operate each
channel. Information is written to the configuration word through the
logic supplied in your ladder program.
dB - (decibel) A logarithmic measure of the ratio of two signal levels.
data word - A 16-bit integer that represents the value of the analog
input channel. The channel data word is valid only when the channel