Rockwell Automation 1769-IF4XOF2 Compact 8-Bit Low Resolution Analog I/O Combination Module - Manual (Page 93)

1 Publication 1769-UM008A-EN-P - November 2001
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 Converter – Refers to the analog to digital converter inherent to
the module. The converter produces a digital value whose magnitude
is proportional to the magnitude of an analog input signal.
alternate last state – A configuration selection that instructs the
module to convert a user-specified value from the channel fault or
program/idle word to the output value when the module enters the
fault or program mode.
analog input module – A module that contains circuits that convert
analog voltage or current 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.
bus connector – A 16-pin male and female connector that provides
electrical interconnection between the modules.
channel – Refers to analog input or output interfaces available on the
module’s terminal block. Each channel is configured for connection to
a variable voltage or current input or output 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.
common mode rejection – For analog inputs, the maximum level to
which a common mode input voltage appears in the numerical value
read by the processor, expressed in dB.
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 – For analog inputs, the voltage difference
between the negative terminal and analog common during normal
differential operation.
common mode voltage range – For analog inputs, the largest
voltage difference allowed between either the positive or negative
terminal and analog common during normal differential operation.