When one hears: Smart Meter, the picture that immediately comes to mind is an electricity meter which can measure the energy consumption of a household, where there optionally are installed PVs at the roof. Somewhere between electricity meters, and sensors (in the broad term) in a sensor network, we have a device that is typically overseen in the smart metering context: a Water Meter. One of the reasons why we do not see these devices as anything even close to smart is because they, in general, are not “smart”.
In the recent years, things have changed a lot though. The meters are being extended with wireless capabilities, either in the form of a module attached directly on top of a plain old meter, “reading” the display and relay its values, or inherently build into the meter itself, as for the Kamstrup Multical 21. Also larger cities are buying into this type of technology. This mainly to cut labor cost, but also for the more advanced meters, to get more fine grained insight into the installation state with leak alarms, etc. One example is New York City .
But what language do these devices speak? At least in EU, the answer is: Wireless M-Bus, a wireless extension of the original M-Bus protocol developed back in the nineties. Wireless M-Bus is specifically designed for battery powered meters. This is seen in the lifetime for these devices: The Multical 21 for example guarantees 16 years, with a broadcast transmission every 16 seconds . That is a total of 1.973.062 transmissions – impressive. No matter how low-power Bluetooth, LTE, Zig-Bee, or any other more general protocol ever becomes, they will hardly be able to beat these numbers. The protocol is not specifically designed for water meters, and other (mainly battery powered) product types within metering also uses the protocol, for example gas meters, or even district heating meters.
Wireless M-Bus is a three-layered protocol: PHL, DLL and APL, and these layers will be analyzed separately in future posts, so stay tuned.