Overview
The Allen-Bradley 1746-NR4 is a four-channel RTD/resistance input module for SLC 500 controllers, converting analog data from RTD units or other resistance inputs into digital form for processing by the controller. This Series B module delivers precise, isolated analog-to-digital conversion for temperature and resistance-based process measurement across industrial automation systems.
Key Features
- Up to 4 RTD/resistance inputs (2-, 3-, or 4-wire connections)
- Interfaces with platinum, nickel, copper and nickel-iron RTDs, and with variable resistance devices such as potentiometers (0 to 3,000Ω maximum)
- Provides on-board RTD temperature scaling in degrees Celsius and degrees Fahrenheit or resistance scaling in ohms
- Uses sigma-delta A/D conversion and digital filtering to deliver accurate temperature and resistance measurements
- Built with broken sensor detection that may indicate a shorted or open circuit; when error is detected, the module’s indication is out of range
- Module does not require an external power supply and it does a self-calibration automatically when the filter frequency, input type, or excitation current, or when a channel is enabled
Technical Specifications
- Input Channels: 4 RTD/Resistance analog inputs
- Resolution: 16 bits maximum
- Response Time: 95% step response of 12–300 ms
- Backplane Current: 50 mA at 5V DC or 50 mA at 24V DC
- Maximum Backplane Power: 1.5 Watts (0.3 W at 5V DC, 1.2 W at 24V DC)
- Operating Temperature: 0°C to 55°C (32°F to 131°F) in most slots; 0°C to 60°C (32°F to 140°F) in the rightmost slot
- Communication: Backplane communication with SLC processor using an image table of 8 input words and 8 output words
- Resistance Range Support: 0–150 Ω, 0–300 Ω, 0–500 Ω, and 0–1000 Ω signals
- Temperature Range: Can measure temperature as low as –200 to 850 degrees Celsius
- A/D Conversion Method: Sigma-delta modulation
- Status Indicators: 5 LED indicators—1 module status indicator and 4 channel indicators, with 1 indicator per channel
Typical Applications
Typical applications include temperature monitoring, displacement measurement, process feedback, and equipment position sensing where high-accuracy RTD inputs are required. The 1746-NR4 is ideal for:
- Thermal process control and monitoring
- HVAC and refrigeration systems
- Food and beverage production
- Pharmaceutical and chemical processing
- Industrial oven and furnace control
- Environmental chamber feedback
Compatibility & Replacements
Compatible With
- Fixed style and modular style SLC 500 controllers
- Rockwell Automation SLC 500 family processors
- RSLogix 500 programming software
- SLC 500 backplane-based systems (I/O rack configuration)
Replaces / Drop-In Replacement For
Verify compatibility with your system integrator before ordering. The 1746-NR4 Series B is a direct replacement for earlier Series A versions where similar RTD input functionality is required.
Works With
- RSLogix 500 and Logix 500 programming platforms
- SLC 500 I/O configuration and ladder logic programming
- Multiple RTD sensor types (Pt100, Pt385, Cu, Ni, Ni-Fe)
- Resistance potentiometer inputs (0–3000 Ω)
