Overview
The Allen-Bradley 1771-IR /D is a Resistance Temperature Detector (RTD) input module engineered for the PLC-5 series. It provides precise temperature measurements across industrial automation, process control, and thermal monitoring applications. The module requires no external power supply and operates as a single-slot I/O module compatible with any 1771 I/O chassis.
Key Features
- Six three-wire RTD input channels for simultaneous temperature measurement
- Supports both platinum (100 ohm) and copper (10 ohm) RTD sensor types
- Temperature output in Celsius or Fahrenheit via 4-digit BCD or 16-bit format
- Open-wire detection for sensor fault identification
- LED status indicators on front panel for real-time diagnostics
- Bidirectional block-transfer communication with PLC processor
- Meets UL Standard 508 and CSA Standard C22.2 No. 142 for safety isolation
Technical Specifications
- Channels: 6 three-wire RTD inputs
- Sensor Types: 100 ohm platinum (α = 0.00385), 10 ohm copper (α = 0.00385)
- Current Load: 800 milliamperes on chassis backplane
- Module Type: Single-slot, no external power required
- Input Scanning: Minimum 50 ms block transfer interval
- Output Format: 4-digit BCD or 16-bit signed magnitude
- Cable Requirement: Three-conductor shielded cable
- Temperature Rate of Change: Rapid changes >10°C/min may temporarily affect performance
- Compatible Chassis: 1771-A1B, A2B, A3B, A4B, and all 1771 I/O frames
- Mounting: Single-slot module in any I/O chassis slot
- Safety Certifications: UL 508, CSA C22.2 No. 142
Typical Applications
- Process heating and cooling systems requiring multi-point temperature control
- Industrial furnaces and ovens with precise thermal management
- HVAC systems in manufacturing facilities
- Packaging machinery with temperature-dependent operations
- Food and beverage processing with regulatory compliance needs
- Pharmaceutical manufacturing requiring accurate temperature logging
Compatibility & Replacements
The 1771-IR /D is compatible with all Allen-Bradley PLC-5 systems and 1771 series I/O chassis. It integrates with RSLogix and Studio 5000 programming environments for ladder logic configuration. The module has been a long-standing component in legacy industrial systems and remains available through authorized distributors as original or serviceable surplus units. When selecting a replacement for older 1771-IR series modules, confirm sensor type requirements (platinum vs. copper) and wiring arm specifications to ensure drop-in compatibility.
