Rockwell 1746-WS Hardy Microprocessor-Based I/O Module – 2 mV/V Strain Gauge, 5 kΩ Input

The Allen-Bradley 1746-WS is a microprocessor-based Weight Scale (WS) input module developed by Hardy Instruments and integrated into the Rockwell Automation SLC 500 family of programmable controller I/O modules. Designed to bridge the gap between industrial weighing hardware and the SLC 500 processor, the 1746-WS accepts low-level analog signals from up to two load cells or strain-gauge transducers and converts them into high-resolution digital weight values that the SLC 500 can use directly in ladder logic. Unlike a conventional analog input module, the 1746-WS is not merely a voltage-measuring device—it is a dedicated weighing subsystem on a single SLC 500 form-factor card, complete with its own microprocessor, signal conditioning, calibration memory, digital filtering, and auto-zero logic.The 1746-WS is built around a microprocessor-based architecture that performs all signal processing locally, relieving the SLC 500 CPU of the intensive mathematical operations required for stable weight calculation. The module continuously samples the load-cell signal at 10 samples per second through a 16-bit analog-to-digital converter, applies programmable digital filtering to suppress mechanical vibration and electrical noise, and presents the resulting weight value to the processor as a standard SLC 500 data table value. This architecture allows the SLC 500 to read a stable, noise-free weight without dedicating scan time to filtering or scaling math. The 1746-WS supports two independent weighing channels, accepts a full-scale input signal of 2 mV/V at 5 kΩ input resistance, and operates from a 120/240 V AC, 50/60 Hz power source.A key differentiator of the 1746-WS is its onboard intelligence. The module stores calibration data internally, supports auto-zero and tare functions, and provides front-panel status indicators for power, calibration status, and signal health. Its IP20-rated enclosure is designed for indoor cabinet installation, with screw-terminal field wiring connections that accept 14–22 AWG conductors. The entire module is hot-swappable—it can be removed and replaced without powering down the SLC 500 chassis, minimizing downtime during maintenance. With the SLC 500 platform now legacy and the 1746-WS no longer in active production, the module circulates primarily as new-surplus and tested take-out stock, remaining an essential spare for the extensive installed base of Hardy-equipped SLC 500 weighing systems in food processing, chemical batching, and material handling applications.

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Description

Technical Specifications

Parameter Name	Parameter Value
Product Model	1746-WS
Manufacturer	Hardy Instruments / Rockwell Automation (Allen-Bradley)
Product Type	Microprocessor-Based Weight Scale Input Module
Compatible Platform	Allen-Bradley SLC 500 Programmable Controller
Number of Channels	2 independent weighing channels
Input Signal Type	Strain-gauge / load-cell mV/V signal
Full-Scale Input	2 mV/V
Input Resistance	5 kΩ
Analog-to-Digital Conversion	16-bit ADC
Sampling Rate	10 samples per second
Power Supply	120/240 V AC, 50/60 Hz
Isolation	1500 V DC between field and logic sides
Calibration	Onboard microprocessor; calibration data stored in module
Signal Processing	Programmable digital filtering, auto-zero, tare
Communication	SLC 500 backplane (proprietary)
Mounting	SLC 500 chassis slot
Terminal Type	Screw terminals, 14–22 AWG field wiring
Enclosure Rating	IP20 (indoor cabinet installation)
Operating Temperature	0°C to +60°C
Storage Temperature	-40°C to +85°C
Relative Humidity	5% to 95% RH, non-condensing
Hot-Swappable	Yes (module can be replaced without chassis power-down)
Status Indication	Front-panel LEDs: power, calibration status, signal health
Physical Dimensions	Standard SLC 500 single-slot module
Country of Origin	USA
Lifecycle Status	Legacy / discontinued; available as new surplus or tested take-out

Main Features and Advantages

Microprocessor-based local signal processing: The standout capability of the 1746-WS is its onboard microprocessor, which performs all signal conditioning, filtering, and scaling locally rather than burdening the SLC 500 CPU. Load-cell signals are notoriously susceptible to mechanical vibration, electrical noise, and thermal drift; the 1746-WS samples at 10 Hz through a 16-bit ADC and applies programmable digital filtering to produce a stable weight value. This allows the SLC 500 to read a clean, scaled weight directly from the module’s data table without dedicating scan time to filtering or scaling math—a significant advantage in high-speed batching applications where the CPU is already occupied with sequencing logic.Dual-channel independent weighing: The 1746-WS supports two completely independent weighing channels on a single SLC 500 slot, effectively providing two dedicated scale inputs for the price and chassis space of one module. Each channel can be calibrated independently with its own zero, span, and filtering parameters. This makes the 1746-WS ideal for applications requiring simultaneous weighing of two ingredients, or separate gross and tare weighments. For machine builders working within the tight chassis-space constraints of the SLC 500 platform, this dual-channel density is a major advantage.Onboard calibration with persistent memory: Unlike passive analog input modules that require the PLC program to store and apply calibration factors, the 1746-WS stores all calibration data internally in non-volatile memory. Zero and span calibration is performed at the module level and survives power cycles without requiring the SLC 500 program to reload calibration constants. The front-panel status indicators provide immediate visual confirmation of calibration status and signal health, allowing maintenance technicians to distinguish between a failed load cell, a broken signal cable, and a module fault without specialized test equipment.Hot-swappable design for minimal downtime: The 1746-WS can be removed and replaced without powering down the SLC 500 chassis. In continuous-process applications where a planned shutdown is difficult to schedule, this hot-swap capability allows a faulty module to be swapped during normal operation, with the SLC 500 automatically recognizing the replacement and resuming normal weighing within seconds. This single feature can mean the difference between a 30-minute maintenance window and an unplanned production halt.