Rockwell Automation 1746-INT4 Thermocouple/MV Isolated/ User Manual - Manual (Page 109)

109 Publication 1746-UM614B-EN-P - September 2007
Glossary
Terms and Abbreviations The following terms and abbreviations are used throughout this
manual. For definitions of terms not listed here refer to the Industrial
Automation Glossary, Allen-Bradley publication AG-7.1.
A/D
Refers to the analog-to-digital converter within the module. The
converter produces a digital value whose magnitude is proportional to
the instantaneous magnitude of an analog input signal.
attenuation
The reduction in the magnitude of a signal as it passes through a
system. The opposite of gain.
channel
Refers to one of four, small-signal analog input interfaces to the
module’s terminal block. Each channel is configured for connection to
a thermocouple or dc millivolt (mV) input device, and has its own
configuration and status words.
chassis
A hardware assembly that houses devices such as I/O modules,
adapter modules, processor modules, and power supplies.
CJC (Cold Junction Compensation)
The means by which the module compensates for the offset voltage
error introduced by the temperature at the junction between the
thermocouple lead wire and the input terminal block (the cold
junction).
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 signal induced in conductors with respect to ground (0
potential).