1756-2WS | Allen-Bradley | ControlLogix Dual-Channel Weigh Scale Module

Configured for high-precision strain gauge signal processing in ControlLogix industrial control networks, the Allen-Bradley 1756-2WS (1756-2WS Dual-Channel Weigh Scale Module) provides direct physical/electrical execution of load cell excitation and bridge signal digitization. This module utilizes two independent scale channels to interface with full Wheatstone bridge strain gauge load sensors, converting millivolt-level bridge imbalances into digital weight data for high-speed processor access.

Hardware Specifications

Industrial Control Deterministic Network Connectivity

The 1756-2WS integrates into the ControlLogix backplane to ensure deterministic data throughput across the system. The module leverages high-speed backplane bus communication velocity to minimize processing latency for weigh-scale values. Users must verify firmware flash compatibility between the module and the host controller to support specific weight-filtering algorithms and calibration routines. I/O density scaling must be calculated based on the 1.0 A current requirement from the 5 VDC backplane rail to prevent power supply overloading when multiple weigh modules are deployed in a single chassis.

Frequently Asked Questions (FAQ)

Q: Does the module support hot-swapping under power?

A: Yes, the 1756-2WS is designed for field hot-swap operations within a ControlLogix chassis. However, ensure that field-side wiring is disconnected or secured before removing the module to prevent electrical damage to the backplane connectors.

Q: Are the channels galvanically isolated from each other?

A: Yes, the module provides independent channel monitoring. Proper shielding of the load cell cables is mandatory to maintain signal integrity and prevent cross-channel interference.

Field Installation Guidelines

• Load Cell Wiring: Connect load cells using high-quality shielded twisted-pair cabling. Terminate the shield at the module’s chassis ground point to mitigate common-mode noise and electromagnetic interference (EMI).
• Excitation and Sensing: Ensure that the load cell wiring configuration (4-wire or 6-wire) is correctly configured in the module software parameters to account for lead-wire resistance compensation.
• Grounding: Mount the module in a ControlLogix chassis that is connected to a low-impedance earth ground. Avoid routing load cell signals near high-voltage motor cables or variable frequency drive (VFD) outputs to prevent signal oscillation.
• Mechanical Seating: Fully insert the module into the chassis slot and lock the latching mechanism to ensure reliable backplane pin contact. Verify that the module is not physically stressed by excessive cable tension at the terminal block.