BECKHOFF KL6781 Bus Terminal M-Bus Master

Description

Designed to facilitate seamless integration of utility metering devices, the Beckhoff KL6781 operates as a single-channel M-Bus master terminal within the standard Beckhoff Bus Terminal system. This module enables direct, bidirectional communication with up to 40 standard M-Bus loads, such as heat, water, electricity, or gas meters, over a single bus segment without requiring external level converters. Operating in master-slave mode via polling, the KL6781 transmits data standard M-Bus physics, enabling consolidated energy management and resource tracking directly from the TwinCAT control environment.

The terminal features a 24-byte process image for inputs and outputs, allowing robust data transfer rates ranging from 300 to 9600 baud. Integration is streamlined through the TwinCAT PLC M-Bus library, which provides specialized function blocks for rapid field configuration. With built-in short-circuit protection and 500 V electrical isolation between the K-bus and the M-Bus physics, the module ensures robust operation and system-wide protection against electrical faults in harsh industrial or commercial environments.

Features

• Single-Channel Architecture: Dedicated M-Bus interface supporting up to 40 standard M-Bus loads (1.5 mA current consumption per load).
• Flexible Baud Rates: Configurable data transfer rates from 300 to 9600 baud (default transmission set to 2400 baud).
• Electrical Isolation: Complete 500 V isolation barrier safeguarding the internal K-bus from the M-Bus network.
• Integrated Protection: Full short-circuit proof design to prevent module failure during field wiring faults.
• Software Compatibility: Programmed and configured directly through TwinCAT using official M-Bus PLC function blocks.

Applications

• Commercial and industrial building automation systems (BAS).
• Sub-metering networks for monitoring water, gas, steam, and electricity consumption.
• Energy management systems (EMS) compliant with ISO 5001 standards.
• District heating stations and utility billing infrastructure.

Technical Specifications

Connections and Interfaces

Installation Guidelines

• Mounting: Mount the terminal vertically on standard 35 mm DIN rails (EN 60715) within an IP20-rated enclosure or control cabinet.
• Wiring: Keep maximum cable lengths on the M-Bus segment below 300 meters. Use shielded twisted-pair (STP) cabling for optimal noise immunity.
• Grounding: Connect the shield connection point directly to a low-impedance functional ground or DIN rail clamp.
• Ventilation: Ensure a clearance of at least 30 mm above and below the terminal block to maintain normal operating temperatures between 0 and 55 degC.