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About M-Bus
The advantages of M-Bus for submetering include its standardized protocol, self-describing values, low power consumption, and simple configuration and installation.
M-Bus står för "Meter-Bus" och är ett standardiserat kommunikationsprotokoll för fjärravläsning och hantering av mätare och sensorer.
The protocol is primarily used in energy and water metering systems, where it enables efficient and reliable communication between various types of meters and data collection units.
M-Bus is a communication technology used for metering and remote reading of, for example, electricity, water, heating, and temperature.
The M-Bus protocol is stable, clear, and provides highly detailed information. However, compared to other technologies, M-Bus can be perceived as slow. M-Bus is therefore best suited for meter readings that can be sent at lower frequencies, such as every quarter, hour, or day. For billing purposes, such as water or electricity consumption, it is often more than sufficient.
M-Bus is a standardized open protocol developed in 1991 for meter data collection in urban environments, but today it is primarily used for sub-metering in properties. Despite its age and tough competition from new technologies, M-Bus remains one of the most common methods for reading meters.
M-Bus comes in two versions: wired and wireless. Wireless M-Bus shares many of the advantages of wired M-Bus, with the difference that you avoid expensive cable installations. In our article series on M-Bus, we will return with a deep dive into wireless M-Bus in a later post.
A wired installation is powered and controlled by an M-Bus master, and since the M-Bus master provides the meters (or loads, as they are called in M-Bus terminology) with power, the number on the loop is limited by the power supply.
The M-Bus master comes in different sizes, and typically 256 meters (loads) can be connected, but it can be expanded with extenders so that more can be collected.
M-Bus combines communication and power supply in two wires. Since installations can vary and it can be difficult to pull pre-assembled connectors through electrical conduits, no standard connector is specified. Furthermore, the wires are "polarity independent," meaning the installer does not need to worry about plus or minus—in other words, it does not matter how the two wires are connected. How the cables are routed and connected is also flexible, allowing for both star and bus topologies. Typically, one cabling setup can support 256 meters.
A common problem in networks is how to address meters. M-Bus has two options for addressing: primary and secondary addressing.
Primary addressing uses a number between 1-250 that must also be unique on the loop, which is why each meter's primary address must be set manually during installation.
With secondary addressing, you instead use an 8-digit number pre-printed on the meter, which is usually the same as the meter number. This method requires no manual configuration and therefore carries a lower risk of errors.
A secondary address is unique in the vast majority of installations, but there is still a small risk that two meters from different manufacturers are delivered with the same secondary address. Therefore, in addition to the secondary address, M-Bus also uses an internationally unique identification.
The unique identification consists of the meter's three-letter manufacturer code, the meter type, the meter generation, and the secondary address. Here is an example of what a unique identification might look like for an electricity meter from ABB: ABB-12345678-Electricity meter-Generation:1.
A major advantage of M-Bus compared to other protocols is that the values sent in M-Bus are self-descriptive. For every value sent from the meter, the meter itself specifies the quantity and unit. The benefit of this is that a new driver is not required for every new meter you want to collect data from. Unfortunately, this falls short when it comes to slightly more complex meters and values, but we will return to this later in our article series.
M-Bus stands for "Meter-Bus" and is a standardized communication protocol for the remote reading and management of meters and sensors.