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M-Bus M-Bus | Devices / Masters Devices / Masters

M-Bus (Meter-Bus)

The M-Bus also known as meter bus is a low cost electronic system for remote meter reading, it's usable for all consumption meters. You only need a computer and one or more smart meter devices and cables to wire them to use this protocol. It's a European standard. This guide gives useful information for you, to help you setup an M-Bus smart meter network in your building.

On this page you will read about M-Bus features, and also discover why it is benefical to use. You also read about how you can build a M-Bus network and what topologies you can use and what errors can occur during measurement.


Figure 1 - M-Bus structure.

Why it is good to use?

With only one cabel pair you can connect all consumption meters of a building. You can reach all of the devices with unique addresses. Reading is fast and precise. Your system will have minimal power consumption.


Figure 2 - Standard M-Bus system with repeaters.

How to build a M-Bus (Meter-Bus) network

An M-Bus network is a great tool to collect data from smart meters. To build an M-Bus network you need to connect the smart meters to a central data collection unit. For the connection a two wire 'bus' can be used. Each device (including the smart meters and the data collection unit can be connected to these two wires as shown on Figure 1 and also on Figure 2.

Smart meters are often referred to as slave devices. Data collection units (personal computers or dedicated data acquisition devices) are referred to as master devices. There can be a single master device and several slave devices on the M-Bus network.

A two wire telephone cable is a good choice for the transmission medium for the M-Bus. The optimal distance can be 350m between the master and slave devices. In a local connection, you can use different kinds of topologies. On the M-Bus network only one device can communicate any given time. This is called a half-duplex connection (Figure 3).


Figure 3 - What is half-duplex?

The following topologies can be used:
  • Star topology: Each component is linked to a central processing unit with an individual transmission line.
  • Bus topology: There is a common transmission line where the components are connected to. It's very cost effective.
You can also combine the star, bus topology together to a more complex network (Figure 4).


Figure 4 - Star bus topology.

M-Bus features

The advantages of M-Bus is that you can use multiple slave devices on a single communication line. The M-Bus network can operate at different speeds. The speed of transmission can be expressed in a measurement called Baud rate. The higher speed the device is set to, the faster you can transfer the data from the slave back to the PC. The negative effect of high speed, is that the length of the communication line must be reduced. If you wish to communicate over a greater distance, you have to lower the baud rate. You can extend the lenght, using repeaters, or you can also get greater distance with lowering data collection units (slaves), but the total lenght should not be greater than 1000 m.

Error processing with M-Bus

With M-Bus you can handle many kinds of errors, detect them and make sure everything went right. You can also choose from different methods to take care of errors, problems. There can be lots of reasons why an error occur, for example electromagnetic interference, inductive coupling at mains frequencies or the cable lenght is not enough then the receiver cannot get the signal. With the data to be transmitted, it also good to have additional informations, so you can detect error and recognise, correct them, M-bus has this feature.

Summary

To sum this short article up, building an M-Bus network is beneficial if you would like to have a fast and precise system for remote meter reading. You can get more informations about M-bus here: The M-Bus: A Documentation. Many devices support this standard and other protocol called Modbus. Modbus is also great and easy to control a remote meter reading system. You can get more informations about Modbus here.

Sources:

  • http://www.m-bus.com
  • https://www.technologyuk.net


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