Description:

The Allen-Bradley 1746-NR4​ is a four-channel RTD and resistance input module from Rockwell Automation, designed for the SLC 500 programmable controller platform. It belongs to the 1746 analog I/O family and converts resistance-based temperature sensor signals directly into digital values that any fixed or modular SLC 500 processor can read from its image table.What distinguishes the 1746-NR4​ from a general-purpose analog input card is that it accepts bare RTD elements — platinum, nickel, copper, and nickel-iron — without any intermediate transmitter or signal conditioner. Each channel is independently configurable for sensor type, wiring topology, temperature units, filtering, and excitation current, so a single module can simultaneously serve four completely different temperature sensors on the same process.

Application Scenarios:

A pharmaceutical manufacturer operated an autoclave served by a SLC 5/03, with four Pt100 sensors monitoring chamber temperature, jacket temperature, product probe temperature, and drain temperature. Each sensor ran through a head-mounted 4–20 mA transmitter into a 1746-NI4 current input module. The architecture worked, but it carried a recurring cost: every transmitter was a calibrated device in the validation scope, and the annual calibration cycle required four instruments to be pulled, documented, and reinstated, with the autoclave out of service for the better part of a shift. Worse, transmitter drift was invisible until calibration day — a transmitter that had drifted 0.4 °C was quietly biasing an entire year of sterilization cycles in a GMP-regulated process.Replacing the transmitters and the NI4 with a single 1746-NR4​ removed an entire instrument layer. The Pt100 elements wired directly to the module’s removable terminal block in 3-wire configuration, and the module handled excitation, lead-resistance compensation, linearization, and conversion internally. The calibration scope shrank from four transmitters plus one analog input card to one module plus the sensors themselves. Because the 1746-NR4​ performs automatic calibration at power-up and on channel enable, the manual trim-pot adjustments that consumed technician time disappeared entirely.This is the pain point the 1746-NR4​ addresses: the hidden lifecycle cost of analog temperature architectures. It applies wherever a SLC 500 needs accurate temperature and the alternative is a chain of transmitters, conditioners, and calibration records — pharmaceutical autoclaves and lyophilizers, food and beverage pasteurizers and retorts, chemical reactor jackets, plastic injection molding barrel and manifold zones, heat treat furnaces and kilns, HVAC and chilled water systems, bearing and winding temperature monitoring on motors and turbines, and water treatment digester temperature control. The 1746-NR4​ also accepts potentiometers and direct resistance inputs, which makes it the natural choice for position feedback from slide-wire transducers and for any resistive sensing element in the 150 Ω to 3000 Ω range.

Parameter: