Product Overview
In the evolution of industrial automation, precise temperature measurement has become a cornerstone of process control and equipment protection. The Allen-Bradley 1746-NR8, part of the Rockwell Automation SLC 500 series, addresses this need with an 8-channel RTD/Resistance Analog Input Module. Designed for both fixed and modular SLC 500 hardware styles, this module accepts signals from a wide range of RTD sensors and direct resistance devices, making it a versatile choice for temperature and displacement monitoring applications.
Technical Specifications Breakdown
Key parameters for the 1746-NR8 are listed below for quick reference:
| Feature | Specification |
|---|---|
| Brand | Allen-Bradley |
| Manufacturer | Rockwell Automation |
| Series | SLC 500 |
| Part Number | 1746-NR8 |
| Module Type | RTD/Resistance Analog Input Module |
| Number of Inputs | 8 |
| Backplane Current (5 Volts) | 100 milliamps |
| Backplane Current (24 Volts) | 55 milliamps |
| Backplane Power Consumption | 1.82W maximum (0.5W at 5V dc, 1.32W at 24V dc) |
| Update Time | 6 milliseconds to 2 seconds |
| Step Response | 60 milliseconds in, 2.5 milliseconds out |
| Resolution | .01 Deg. Celcius |
| Operating Temperature Range | 32 to 140 degrees Fahrenheit |
| Storage Temperature | -40 to 85 degrees Celsius |
Industry Applications
This module is primarily used for temperature measurement in industrial processes, leveraging RTD sensors such as Platinum (385) and Platinum (3816) for high accuracy. The resistance input capability also supports displacement measurement in mechanical systems, where changes in resistance reflect movement. Typical applications include monitoring motor winding temperatures, bearing temperatures in rotating equipment, and position feedback in linear actuators.
Installation & Setup Guidance
Install the module in any I/O chassis slot except Slot 0, which is reserved for the processor. The module is powered via the backplane, so no external power supply is needed. For 2-wire RTD sensors, use Belden 9501 shielded cable or equivalent to minimize lead resistance effects. For 3-wire or 4-wire configurations, Belden 9533 or Belden 83503 cable is recommended. Each terminal on the Removable Terminal Block (RTB) accepts only one wire. The module supports 2-wire, 3-wire, and 4-wire RTD connections, with 4-wire offering the highest accuracy.
Maintenance & Reliability
Periodically inspect the module and terminal block connections for signs of corrosion or loose wiring. Ensure the operating environment stays within the specified temperature range of 32 to 140 degrees Fahrenheit. The module performs auto-calibration at power-up and can be programmed to recalibrate every 5 minutes, maintaining measurement accuracy over time.
Compatibility & Integration
The 1746-NR8 is designed exclusively for SLC 500 systems, compatible with both fixed and modular hardware styles. It interfaces with a wide range of RTD sensors including Platinum (385), Platinum (3816), Copper (426), Nickel (618), Nickel (672), and Nickel Iron (518). Direct resistance inputs from 0 to 150 Ohms, 0 to 500 Ohms, 0 to 1000 Ohms, and 0 to 300 Ohms are also supported.
Selection Guide & Purchasing Advice
When selecting the 1746-NR8, verify that your SLC 500 system has an available slot (any slot except Slot 0). Ensure the backplane power supply can provide the required 100 mA at 5VDC and 55 mA at 24VDC. For reliable sourcing, purchase from SpareTechPLC, a trusted supplier of industrial automation parts. Please verify current lifecycle status and availability with SpareTechPLC before ordering.
Troubleshooting & Common Issues
If the module does not communicate, check the backplane connection and ensure the chassis slot is not Slot 0. For inaccurate readings, verify RTD sensor wiring (2-wire, 3-wire, or 4-wire) and cable type. Long cable runs on 2-wire RTDs can reduce accuracy; use lower gauge wire if necessary. Monitor the LED status indicators for channel and module status.
