1. Background

As China is implementing regulations to install one meter in each household, building developers as well as utilities are becoming more and more interested to rely on Automatic Meter Reading (AMR) system to collect data from all type of meters: heat meters, hot and cold water meters, gas meters and electricity meters. The AMR system will then allow a quick and inexpensive reading of all types of meters while avoiding unnecessary intrusion in the premises of the customers.
 
The needs of the building developers or utilities can be summarized as below:

-it shall be possible to read a large number of meter indexes from a central point located either at the building control room or from a remote point.

-data collection of all meters shall be possible at any time and in a fast way

-as meter indexes are used for billing purposes, data transmission shall be accurate and free of any reading error

-it shall be possible to connect meters from any manufacturer brands on the same system, and to use a single software to read them all.

-installation of the AMR network shall be simple, inexpensive and easily expandable

-the reading network shall consume minimum power from the meters in order to limit the impact on the meters’ battery lifetime.

-the system AMR shall also offer the reading of all the meter data. For example it shall be possible to read for a heat meter: heating energy index, cooling energy index, cumulated volume, instant supply and return temperatures, instant flow-rate, instant power, backflow detection, alarms, etc…

None of the many already existing bus systems was able to fulfill all these constraints.
In the early 90’s a user group was created in Europe to work on a special standard for the remote reading of meters: the M-Bus ("Meter-Bus"). The details of the standard were designed by a German university professor in association with experts of Texas Instruments Co.
The m-bus standard was later officially adopted in the European standard EN1434-3:1997 and in the new Chinese standard for AMR system JG/T162-2004.

2. M-bus details

The M-Bus is a hierarchical system, with communication controlled by a master (Central Allocation Logic). The M-Bus consists of the master, a number of slaves (the meters) and a two-wire connecting cable.