Product Overview

The Allen-Bradley 1756-IT6I​ is a high-speed, isolated Thermocouple / Millivolt Analog Input Module within Rockwell Automation’s ControlLogix® 1756 I/O platform, specifically engineered to acquire low-level DC millivolt signals and thermocouple readings with exceptional resolution and noise rejection. Although often grouped with temperature modules, the Allen-Bradley 1756-IT6I​ is uniquely valued for its ±50 mV, ±100 mV, and ±250 mV DC millivolt ranges, making it equally suitable for direct connection to weighing transducers, pressure strain gauge amplifiers, and custom analog transmitters that output low-level millivolt signals, in addition to Type J/K/T/N/E/S/R/B thermocouples. The module provides six independently configurable input channels, each with its own 24-bit A/D converter and ±500 V DC isolation (1500 V AC tested) between field wiring and the ControlLogix backplane, ensuring signal integrity in electrically noisy industrial environments.The Allen-Bradley 1756-IT6I​ supports both single-ended and differential input wiring, cold-junction compensation (CJC) via an onboard sensor for thermocouple applications, and open-sensor detection for all thermocouple and mV ranges. Data is updated to the ControlLogix controller at a configurable rate (typical update times of 20 ms to 750 ms depending on filter setting and number of enabled channels), with 16-bit usable resolution for mV ranges and scaling directly into engineering units (e.g., mV, °C, °F) via the module’s configuration in Studio 5000 Logix Designer®. Each channel can be individually enabled/disabled, linearly scaled, and alarmed (high/low/high-high/low-low with latching options), with comprehensive diagnostic status available through controller tags. The Allen-Bradley 1756-IT6I​ draws backplane power (typically 170 mA @ 5 V DC, 90 mA @ 24 V DC) from the 1756 chassis and mounts in any available slot of a 1756-Ax series chassis, occupying a single slot and appearing as a configurable module in the I/O tree with automatically generated alias tags for each channel’s raw data, scaled engineering value, and status bits.With cULus Listed, CE, C-Tick, and FM Class I Division 2 approvals (on applicable series), the Allen-Bradley 1756-IT6I​ is the preferred choice for applications requiring precise low-level analog acquisition—whether for scientific-grade temperature profiling, weigh-scale millivolt input, or high-accuracy process variable monitoring—within a modern DCS-style ControlLogix architecture.

Technical Specifications

Main Features and Advantages

High-resolution millivolt and thermocouple acquisition: The Allen-Bradley 1756-IT6I​ employs 24-bit sigma-delta A/D converters on each channel, delivering 16-bit effective resolution even on the sensitive ±50 mV range—critical for weigh-scale load cell mV/V outputs or micro-voltage process signals. This allows the Allen-Bradley 1756-IT6I​ to resolve changes as small as 1.5 µV on the ±50 mV span, far exceeding the capability of standard ±10 V analog input modules.Channel-level configuration flexibility: Every one of the six inputs on the Allen-Bradley 1756-IT6I​ can be independently assigned as thermocouple (any T/C type) or mV/voltage range, with its own filter time constant, engineering unit scaling (offset/gain or 2-point linearization), alarm limits, and alarm action (latch/unlatch). This means a single module can simultaneously monitor a Type K thermocouple on Ch0, a ±100 mV weigh-cell signal on Ch1, and a ±250 mV tank level transmitter on Ch2—all with individually tailored scaling and alarming.Advanced diagnostics and open-sensor detection: The Allen-Bradley 1756-IT6I​ continuously monitors each channel for open-circuit (broken wire / burnt-out thermocouple), overrange, underrange, and CJC sensor failure. Diagnostic conditions are reported through dedicated controller tags (e.g., Local:1:I.Ch0DataFault, Local:1:I.Ch0Limits.HighHigh) and can drive alarm logic or HMI indications without additional hardware. The module also provides a module-level fault bit and specific fault codes accessible via GSV instructions.Galvanic isolation for noise immunity: Each bank of three channels on the Allen-Bradley 1756-IT6I​ is galvanically isolated from the ControlLogix backplane and from other channel banks (500 V DC working, 1500 V AC test). This isolation suppresses ground loops and common-mode noise—frequent problems when measuring low-level analog signals in plants with mixed AC drives and DC controls—and protects the sensitive measurement circuitry from transient overvoltages on the field side.Direct engineering-unit scaling in the module: Rather than requiring ladder-logic scaling routines, the Allen-Bradley 1756-IT6I​ can be configured to output a floating-point engineering value (e.g., millivolts, °C, °F, or user-defined EU such as kg via mV-to-mass scaling) directly into the controller tag (Local:x:I.Ch0Data). This reduces scan overhead, simplifies program structure, and ensures consistent scaling across all instances of the module in a project.Seamless ControlLogix integration with automatic tag generation: Once the Allen-Bradley 1756-IT6I​ is added to the I/O Configuration tree in Studio 5000 Logix Designer, the software auto-creates a tag structure containing raw counts, scaled engineering value, alarm status bits, fault bits, and module health—eliminating manual tag definition and reducing configuration errors in large I/O projects.