Rockwell Automation 1769-IR6 Compact I/O 1769-IR6 RTD/Resistance Input Module - Manual (Page 111)

Rockwell Automation Publication 1769-UM005B-EN-P - March 2012 111
Glossary
The following terms and abbreviations are used throughout this manual. For
definitions of terms not listed here refer to the 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.
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 input interfaces available on the module’s terminal block.
Each channel is configured for connection to a thermocouple or millivolt
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.
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 (CMMR) – 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 – The voltage difference between the negative
terminal and analog common during normal differential operation.
common mode voltage range – The largest voltage difference allowed
between either the positive or negative terminal and analog common during
normal differential operation.
configuration word – Word containing the channel configuration
information needed by the module to configure and operate each channel.
cut-off frequency – The frequency at which the input signal is attenuated 3
dB by a digital filter. Frequency components of the input signal that are below
the cut-off frequency are passed with under 3 dB of attenuation for low-pass
filters.