Product Overview

The Allen-Bradley 1794-IR8 is a high-density, 8-channel analog input module designed for precision temperature sensing within the FLEX™ I/O platform. This module converts resistance signals from Resistance Temperature Detectors (RTDs) or direct ohm inputs into digital data for a programmable controller. Engineered for versatility, it supports a broad range of industrial RTD standards, including Platinum, Nickel, Copper, and Nickel-Iron sensors.

The 1794-IR8 is an ideal solution for process industries that require localized temperature monitoring without the need for extensive long-distance sensor wiring. It integrates seamlessly onto a 1794 terminal base (such as the 1794-TB3 or 1794-TB3S), providing a compact footprint for DIN-rail or panel-mounted applications. With 16-bit resolution, this module is specifically tailored for critical temperature control loops in chemical processing, thermal management, and pharmaceutical manufacturing.

Advanced Measurement and Noise Immunity

The 1794-IR8 is optimized for stable operation in electrically "noisy" factory environments where electromagnetic interference can compromise signal integrity.

• High-Resolution Digitization: Utilizes a 16-bit Sigma-Delta converter to ensure granular data capture across the entire input range.

• Redundant Noise Rejection: Features a sophisticated digital filter providing 60dB of common-mode rejection at 60Hz, effectively neutralizing AC line interference.

• Dual Operating Modes: Offers a "Normal Mode" for standard high-speed updates and an "Enhanced Mode" for maximum precision, achieving an accuracy rating as fine as 0.01% of full scale.

• Sensor Compatibility: Accommodates multiple standards, including 100Ω Platinum (Alpha 385 and 3916), 120Ω Nickel, and 10Ω Copper sensors.

• Flexible Scaling: Supports a wide resistance input range from 1 to 433 ohms, allowing it to be used for specialized potentiometer or resistive position sensing.

Technical Specifications

• Manufacturer: Allen-Bradley (Rockwell Automation)

• Model Number: 1794-IR8

• Number of Inputs: 8 Channels (Non-isolated)

• Resolution: 16-bit

• Excitation Current: 718.36 µA (typical)

• Isolation Voltage: 707V DC (Continuous)

• Data Format: 16-bit 2's Complement or Binary

• Throughput Rate: Programmable from 28ms to 650ms (for all 8 channels)

• Power Requirements: 24V DC nominal (10.0V–31.2V DC range)

• Backplane Current: 20mA @ 5V DC

• Dimensions: 6.2 x 5.2 x 9.7 cm

• Weight: 0.15 kg (0.33 lbs)

System Reliability and Safety Features

• Intelligent Diagnostics: The module provides real-time detection for open-circuit (sensor break) or short-circuit conditions, instantly notifying the controller to trigger safety interlocks.

• Overvoltage Protection: Designed to withstand continuous overvoltages of up to 35V DC or 25V AC, preventing hardware failure during field wiring faults.

• Calibration-Free Design: Comes factory-calibrated to maintain long-term stability, reducing the need for periodic field maintenance.

• Extended Thermal Stability: Compensates for cold-junction and ambient drift across a wide operating temperature range of -20°C to +55°C (-4°F to +131°F).