Allen-Bradley 1769-2WS Compact I/O Weigh Scale Module

The Allen-Bradley 1769-2WS, also cataloged as the 1769-2WS Dual-Channel Weigh Scale Interface, operates as a dedicated hardware component for strain gauge-based load cell data acquisition within Compact I/O platforms. Configured for direct physical connection to weigh sensors, the device samples physical force signals and transfers calibrated data registers directly to a CompactLogix or MicroLogix 1500 controller across the system backplane.

Hardware Specifications

Backplane Bus Communication & I/O Density Scaling

The weigh module interfaces with the processor via the native backplane bus communication velocity. It utilizes a 24-bit internal Analog-to-Digital Converter (ADC) to transform millivolt-level strain gauge readings into digital values, managing real-time data streaming without requiring external transmitters. This configuration maximizes local I/O density scaling by supporting up to four 350-ohm load cells per channel on two fully independent circuits. The 1500 VDC isolation barrier separates field-side sensor loops from the digital logic bus, preventing high-frequency common-mode noise propagation across deterministic networks.

Frequently Asked Questions

Q: What is the maximum distance supported between the 1769-2WS module and the connected load cells?

A: The physical distance depends on wire gauge and ambient electrical noise, but standard implementations require 6-wire shielded cable for distances exceeding 15 meters to offset excitation voltage drops through automatic remote sensing.

Q: Can this module operate in an I/O bank located away from the primary controller?

A: Yes. The module is fully compatible with the 1769-AENTR Ethernet adapter, allowing installation in decentralized remote I/O configurations across deterministic EtherNet/IP networks.

Field Installation Guidelines

• Secure the module onto a 35mm DIN rail or panel mount plate, verifying that the adjacent bus levers click completely to lock the physical backplane contacts.
• Route all low-level load cell signal wiring inside dedicated, grounded steel conduits away from high-voltage AC motor lines or variable frequency drive cables.
• Connect the load cell cable shield explicitly to the local enclosure subpanel earth terminal, ensuring the shield remains ungrounded and isolated at the load cell body.
• Verify that the total current draw of all combined modules in the local bank does not exceed the maximum rating of the 1769 power supply unit.