Topology
Two wires
A wired bus simplifies cabling and allows Slave devices to be powered from the master.
m-bus.info · documentation and support
M-Bus technical documentation for integrators.
Materials for automation engineers, BMS/SCADA integrators and metering system designers. This page summarizes wired M-Bus basics, the assumptions behind M-Bus 10/200/400 converters, RS-485 integration and the use of an M-Bus Slave input in repeater mode.
M-Bus in practice
M-Bus / Meter-Bus is used for wired reading of electricity, heat, water, gas and other metering devices in fixed installations.
Communication
Half-duplex
The master controls requests, while Slave devices respond according to protocol and addressing.
Sizing
Unit loads
The converter limit should be treated as a unit-load budget, not only as a raw count of physical meters.
Integration architecture
The M-Bus 10/200/400 family is planned to connect an RS-485 host system with an M-Bus Master segment and support repeater operation via an M-Bus Slave input.
PLC / BMS / SCADAThe host system sends frames over RS-485.
M-Bus converterThe device provides bus power and M-Bus Master physical levels.
Slave metersEnergy, utility and sensor devices respond to master requests.
In repeater mode, the upstream master sees the converter's M-Bus Slave input, while the output side creates a local segment with its own current budget.
Model selection
First sum the unit loads of the meters, then add a design reserve and check addressing, cabling and readout timing requirements.
| Model | M-Bus capacity | Host interface | Purpose |
|---|---|---|---|
| MBS-10 | M-Bus 10 · up to 10 Standard Loads | RS-485 + M-Bus Slave | Small installations and pilots. |
| MBS-200 | M-Bus 200 · up to 200 Standard Loads | RS-485 + M-Bus Slave | Buildings, industry, BMS. |
| MBS-400 | M-Bus 400 · up to 400 Standard Loads | RS-485 + M-Bus Slave | Large facilities and extended segments. |
Integrator checklist
Data needed before sizing or commissioning a segment.
Meters
Model, manufacturer, device count, unit load and primary or secondary address.
Cabling
Cable lengths, cross-sections, topology, existing joints and possible interference sources.
System
RS-485 host, baud rate, frame format, reading schedule and diagnostic requirements.
Technical FAQ
Starter answers for engineers integrating devices in an installation.
Are M-Bus and Wireless M-Bus the same?
No. This documentation is about wired M-Bus, the cable-based bus. Wireless M-Bus is the radio variant.
Does a 200 limit always mean 200 meters?
As a working assumption yes for standard-load meters, but actual projects must sum the real unit loads from meter datasheets.
Why use an M-Bus Slave input?
It allows the converter to operate as an element extending a segment, effectively an M-Bus repeater.
Need technical support?
Send the topology description, meter list and expected readout method.