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Module Operation
When the module receives a differential input from an analog device, the
module's circuitry multiplexes the input into an A/D converter. The converter
reads the signal and converts it as required for the type of input. The module also
continuously samples the CJC sensors and compensates for temperature changes
at the terminal block cold junction, between the thermocouple wire and the
input channel.
16-pin Backplane
Controller
Connector
1769 Bus
Module
ASIC
Data
Module
Status
Module
Configuration
Data
+24V DC
24V GND
Each channel can receive input signals from a thermocouple or millivolt analog
input device, depending upon how you configured the channel.
When configured for thermocouple input types, the module converts the analog
input voltages into cold-junction compensated and linearized digital temperature
readings. The module uses the National Institute of Standards and Technology
(NIST) ITS-90 standard for linearization for all thermocouple types ( J, K, T, E,
R, S, B, N, C).
When configured for millivolt inputs, the module converts the analog values
directly into digital counts.
Rockwell Automation Publication 1769-UM004B-EN-P - March 2010
Opto--
couplers
(3)
Microprocessor
Differential
A/D
8:1
Converter
Multiplexer
Circuits
+5V
+15V
GND
-15V
Isolated Power
Supply
Overview
18-pin Terminal Block
6 Differential
Input
Thermocouple/mV
Protection
Inputs
Circuitry
CJC Sensors
Chapter 1
15
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