Product Overview – Allen‑Bradley 1756‑IT6I2 ControlLogix Analog Input Module

The Allen‑Bradley 1756‑IT6I2 is a high-performance ControlLogix analog thermocouple input module designed for precise temperature measurement in demanding industrial environments. As part of Rockwell Automation’s trusted I/O portfolio, this module delivers six individually isolated input channels and two dedicated cold‑junction compensation (CJC) sensors, ensuring reliable data acquisition even in electrically noisy settings. Whether you are upgrading an existing ControlLogix system or building a new distributed I/O architecture, the 1756‑IT6I2 offers the flexibility, accuracy, and ruggedness required for critical thermal monitoring applications.

Technical Specifications

• Input Channels: 6 individually isolated thermocouple/millivolt inputs + 2 CJC sensors

• Compatible Thermocouple Types: B, C, D, E, J, K, L (TXK/XK), N, R, S, T

• Input Ranges & Resolution:

  • High‑resolution range: –12 to 30 mV with 0.7 µV/bit

  • Standard range: –12 to 78 mV with 1.4 µV/bit

  • 16‑bit overall resolution

• Linearization Standard: ITS‑90 for superior temperature accuracy

• Accuracy (CJC): ±0.3 °C (local and remote)

• Input Impedance: >10 MΩ

• Overvoltage Protection: 120V AC/DC (maximum)

• Noise Rejection:

  • Normal mode: 60 dB at 60 Hz

  • Common mode: ≥160 dB at 600V AC/60 Hz with 100Ω differential resistance

• Settling Time: >80 ms to 5% of full scale

• Channel Bandwidth: 15 Hz

• Offset Drift: 0.5 µV/°C

• Open‑Circuit Detection: Positive full‑scale reading within 2 seconds

• Data Formats: Selectable integer mode (left‑justified, 2’s complement) or IEEE 32‑bit floating‑point mode

• Digital Filter: Available only in floating‑point mode (via application)

• Backplane Power Consumption:

  • 5V DC: 200 mA

  • 24V DC: 150 mA (total max dissipation: 4.6 W)

• Thermal Dissipation: 15.7 BTU/hour

• Module Scan Time:

  • Integer (millivolt): 10 ms min

  • Floating‑point (millivolt): 25 ms min

  • Floating‑point (temperature): 50 ms min

Installation & Wiring Guide

The 1756‑IT6I2 mounts directly into any slot of a ControlLogix chassis. For signal wiring, you must use the dedicated removable terminal block (RTB) – only the 1756‑TBNH (or 1756‑TBSH) is compatible. Ensure the chassis power is off before inserting or removing the module. When connecting thermocouple wires, maintain proper polarity and use shielded cables to preserve signal integrity. The module automatically detects open‑circuit conditions and reports a positive full‑scale value within 2 seconds, aiding rapid troubleshooting. For optimal CJC accuracy, position the local CJC sensor away from heat‑generating components inside the enclosure.

Package Contents (Hardware Only)

• 1 × Allen‑Bradley 1756‑IT6I2 analog input module

• 1 × Removable Terminal Block (RTB) – 1756‑TBNH (included)

• 1 × Installation instructions leaflet

• Anti‑static packaging for safe transport

3–5 Frequently Asked Questions (FAQ)

Q1: Can the 1756‑IT6I2 be used with both grounded and ungrounded thermocouples?
Yes, the 1756‑IT6I2 supports both grounded and ungrounded thermocouple types across all compatible sensor families (B, E, J, K, etc.). The isolated inputs help mitigate ground‑loop errors.

Q2: What is the difference between integer and floating‑point data formats on the 1756‑IT6I2?
Integer mode offers faster scan times (10 ms for millivolt) and left‑justified 2’s complement output. Floating‑point mode provides IEEE 32‑bit values and enables the digital filter feature, but increases scan time to 25–50 ms depending on the unit selected.

Q3: Which RTB is required for the 1756‑IT6I2? Can I use a standard 1756‑TBS6?
No. The 1756‑IT6I2 specifically requires the 1756‑TBNH or 1756‑TBSH RTB. Using an incompatible terminal block may damage the module or cause faulty readings.

Q4: How do I configure the CJC sensor for remote operation?
The module automatically uses the onboard local CJC by default. For remote CJC, you must wire an external CJC sensor to the dedicated terminals and configure the channel accordingly in your Studio 5000 Logix Designer application.

Q5: What is the maximum temperature range I can measure with the 1756‑IT6I2 using a K‑type thermocouple?
With a K‑type thermocouple and ITS‑90 linearization, the 1756‑IT6I2 supports measurement from approximately –270 °C to +1372 °C, depending on the sensor’s actual characteristics and the selected input range.