Product Overview

The 1756-IT6I2 is an enhanced isolated thermocouple and millivolt input module for the Allen-Bradley ControlLogix platform, manufactured by Rockwell Automation. It provides six individually isolated input channels capable of directly interfacing with thermocouples or accepting low-level millivolt signals, making it the higher-accuracy variant within the ControlLogix thermocouple module family. The 1756-IT6I2 is distinguished from the standard 1756-IT6I by its dual cold junction sensors, which reduce cold junction compensation error to approximately 0.3°C compared to the 3.2°C maximum error of the single-sensor design.

Within a ControlLogix chassis, the 1756-IT6I2 functions as a specialized analog input module for temperature measurement in processes where thermocouples are the primary sensing element. Each channel supports input ranges of -12 to 78 mV and -12 to 30 mV, with 16-bit resolution and sensitivity of 1.4 microvolts per bit on the standard range. The module linearizes thermocouple signals into temperature values in Celsius or Fahrenheit, supporting thermocouple types B, C, E, J, K, N, R, S, T, D, and L (TXK/XK). Rockwell Automation discontinued the 1756-IT6I2 on March 31, 2017, and it is no longer available for sale from the manufacturer.

 

Technical Specifications

Parameter Name	Parameter Value
Product Model	1756-IT6I2
Manufacturer	Rockwell Automation / Allen-Bradley
Product Type	Enhanced Isolated Thermocouple/Millivolt Input Module
Input Channels	6, individually isolated
Input Ranges	-12 to 78 mV; -12 to 30 mV
Resolution	16 bits (1.4 µV/bit standard; 0.7 µV/bit high-resolution)
Thermocouple Types	B, C, E, J, K, N, R, S, T, D, L
Cold Junction Sensors	2 integrated sensors
Cold Junction Accuracy	Approximately ±0.3°C
Isolation	250V continuous between inputs
Backplane Current (5.1V DC)	200 mA
Backplane Current (24V DC)	150 mA
Power Dissipation	4.6 W
Terminal Block	1756-TBNH (20-pin, sold separately)
Lifecycle Status	Discontinued (March 31, 2017)

 

Main Features and Advantages

Dual cold junction sensors for superior compensation accuracy: The 1756-IT6I2 incorporates two integrated cold junction sensors on the removable terminal block, a design improvement over the single-sensor 1756-IT6I. This dual-sensor arrangement reduces the potential cold junction compensation error from as much as 3.2°C on the standard module to approximately 0.3°C on the 1756-IT6I2. For temperature-critical processes where thermocouple accuracy directly affects product quality or safety margins, this tenfold improvement in cold junction error represents a meaningful performance gain.

Extended thermocouple type support: Beyond the common industrial types (J, K, T, E, N, B, R, S), the 1756-IT6I2 also supports type C and type D thermocouples, as well as type L (TXK/XK). These additional types extend the module’s applicability to high-temperature measurement applications where tungsten-rhenium thermocouples (types C and D) are required, such as vacuum furnaces and certain aerospace processes.

Comprehensive diagnostic and alarm features: The 1756-IT6I2 provides wire-off detection, under-range and over-range detection, process alarms (high-high, high, low, low-low), and rate alarms with configurable deadbands and latching behavior. These diagnostics are configured through the Studio 5000 Logix Designer environment, with alarm status available in the controller tag database for use in operator alerts and interlock logic. The module also supports real-time sampling (RTS) with configurable periods from 25 ms to 10,000 ms, and digital notch filtering to attenuate line-frequency noise.