Rockwell Automation 1769-IT6 Compact I/O 1769-IT6 Thermocouple/mV Input Module - Manual (Page 15)

Rockwell Automation Publication 1769-UM004B-EN-P - March 2010 15
Overview Chapter 1
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.
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.
18-pin Terminal Block
16-pin Backplane
Connector
1769 Bus
ASIC
Opto--
couplers
(3)
A/D
Converter
Differential
8:1
Multiplexer
Circuits
Input
Protection
Circuitry
Microprocessor
6 Differential
Thermocouple/mV
Inputs
CJC Sensors
+24V DC
24V GND
Isolated Power
Supply
+5V +15V GND -15V
Module
Data
Module
Status
Module
Configuration
Data
Controller