The Allen-Bradley 1746-NR4, also cataloged as the 1746-NR4 RTD/Resistance Analog Input Module, operates as a dedicated hardware component for direct thermal sensor signal acquisition and resistance measurement within SLC 500 rack assemblies.
Hardware Specifications
Parameter
Specification
Brand
Allen-Bradley
Model
1746-NR4
Origin
USA
Weight
0.23 kg (0.50 lbs)
Dimensions
Single-slot SLC 500 chassis footprint
Operating Temp
0 to 60 deg C (32 to 140 deg F)
Power Consumption
Standard backplane power draw
Analog Inputs
4 channels
Input Type
RTD / Resistance
Backplane Current
50 mA at 5 VDC
Filter Frequency
2.62 to 65.5 Hz
Storage Temp
-40 to 85 deg C (-40 to 185 deg F)
Chassis Location
Any slot except Slot 0
Deterministic Backplane & I/O Density Scaling
The 1746-NR4 translates raw field signals from resistance temperature detectors into processed digital formats for transfer across the internal SLC 500 backplane. Built-in digital filtering (2.62 to 65.5 Hz) suppresses industrial electrical noise while preserving fast analog-to-digital update execution. High firmware flash compatibility ensures real-time scaling and linearization of process variables, maintaining low latency and stable I/O density scaling across expanded multi-chassis architectures.
Frequently Asked Questions
Q: Can the 1746-NR4 module be positioned in Slot 0 of an SLC 500 rack?
A: No, Slot 0 is strictly designated for the SLC 500 system CPU processor. The 1746-NR4 can be placed in any remaining open slot in the local chassis.
Q: What is the backplane current draw for the 1746-NR4 module?
A: The module draws 50 mA from the 5 VDC backplane rail, which must be factored into system power supply sizing calculations.
Q: How does the configurable filtering frequency range impact signal processing?
A: The adjustable 2.62 to 65.5 Hz filter allows operators to trade off response time against noise immunity, eliminating line-frequency interference in high-noise electrical environments.
Field Installation Guidelines
Always disconnect power to the SLC 500 chassis before inserting or removing the 1746-NR4 card edge connector. Verify physical keying on the chassis slot to prevent backplane bus pin bending during installation.
Use twisted-pair, overall shielded instrument cable (such as Belden 9501 for 2-wire RTDs or Belden 9533 for 3-wire/4-wire configurations) for field wiring. Land cable shields strictly at a single enclosure protective earth ground bus to prevent ground loop noise. Keep low-level RTD wiring physically isolated from high-voltage AC conductors and motor drive outputs within wire duct runs.
