1756-IR6I Allen-Bradley ControlLogix Isolated RTD Input Module

Product Overview

The 1756-IR6I is a high-precision analog input module designed by Allen-Bradley for the ControlLogix system. Featuring 6 individually isolated channels, this module provides accurate temperature measurement and resistance monitoring in demanding industrial environments.

Engineered with a 16-bit Sigma-Delta analog-to-digital converter, the 1756-IR6I supports 100, 200, 500, and 1000 Ohm Platinum RTD sensors as well as direct ohm resistance ranges up to 4,000 Ohms. Individual channel-to-channel isolation eliminates ground loop interference, ensuring reliable data acquisition across complex process networks.

Technical Specifications

Diagnostic & Filtering Capabilities

• Open-Circuit Detection: Automatically senses broken RTD lead wires or sensor element failure and sets diagnostic status flags in controller tags.
• Channel-to-Channel Isolation: 50V continuous basic insulation prevents common-mode noise propagation between field sensors.
• Digital Filtering: Onboard Sigma-Delta filtering reduces 50/60 Hz line noise, achieving sub-0.1% calibrated measurement accuracy.
• Under/Over-Range Alarming: Dynamic software alarms trigger immediate notification during out-of-spec process temperature spikes.

Application Scenarios & System Compatibility

• Turbine Bearing Temperature Monitoring: Connects directly to multi-point platinum RTD elements in power generation plants.
• Petrochemical Reactor Skid Control: Measures high-precision thermal profiles across hazardous processing zones without interposing transmitters.
• Pharmaceutical Batch Sterilization: Delivers high-resolution 16-bit temperature data for critical FDA compliance logging.

Installation & Wiring Best Practices

• Terminal Block Keying: Configure mechanical RTB keying stops on the 1756-TBNH or 1756-TBSH block to prevent miswiring.
• Shielded Cabling: Use Category 2 individual shielded twisted-pair lead wires grounded at one end to minimize high-frequency noise EMI.
• Hot-Swappable RIUP: Supports Removal and Insertion Under Power (RIUP) for rapid maintenance without stopping the backplane.

Packaging, Logistics & Warranty

• Package Contents: 1x Allen-Bradley 1756-IR6I module sealed in anti-static protective packaging.
• Global Express Delivery: Ships via DHL, FedEx, or UPS within 24 to 48 hours of order confirmation.
• Factory Warranty: Fully covered by a 12-month quality assurance replacement warranty.

Engineering Procurement & Selection Guide

• Confirm Sensor Resistance: Ensure your field RTD element type matches supported 100/200/500/1000 Ohm Platinum specs.
• Assess Lead Wire Resistance: Choose 3-wire or 4-wire RTD configurations to compensate for long field cable runs.
• Order Terminal Block Separately: Remember that removable terminal blocks (1756-TBNH / 1756-TBSH) are sold separately from the card.

Frequently Asked Questions (FAQ)

Q: What is the main advantage of choosing the 1756-IR6I over the standard non-isolated 1756-IR6T module?

A: The isolated card features full point-to-point galvanic isolation, which prevents ground loops and electrical interference when sensors share different ground references.

Q: How do I configure floating-point versus integer data formats for temperature reads?

A: Configuration is handled via Studio 5000 / Logix Designer module properties, where you select IEEE 32-bit floating-point or 16-bit left-justified integer modes.

Q: What causes an open-wire fault flag on a specific channel?

A: This occurs when field wire resistance exceeds upper limits, a conductor snaps, or the connected RTD element burns out.

Q: Can this unit measure pure resistance transducers without converting to temperature units?

A: Yes, you can set the channel configuration directly to resistance mode (1–87 Ω, 2000 Ω, or 4000 Ω ranges).

Q: What is the recommended calibration interval for high-precision thermal applications?

A: Factory specifications recommend a 6-month calibration interval to maintain accuracy better than 0.1% of span.

Global PLC Spare HUB's Insight

During a field overhaul at a chemical processing plant, a customer reported fluctuating, erratic readings on two channels of a 1756-IR6I card installed on a long-distance reactor bed monitoring line.

Our technical specialists audited the installation and discovered that the technician had tied the sensor shields at both the field junction box and the PLC rack, creating a subtle ground loop. Additionally, the lead wire compensation in Studio 5000 had not been performed following a wire extension. Once we removed the extra shield ground, re-calibrated the channel offsets, and verified the 16-bit Sigma-Delta filtering parameters, the temperature signals stabilized immediately with zero drift. Proper grounding and lead-wire calibration are essential for achieving sub-degree precision!

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