Meter protocols¶
In the following article, you will become acquainted with the meter protocols the OneMeter Device provides compatibility with.
How to recognize them?¶
Many meters have the protocol name engraved on the plastic cover. You probably deal with:
- BLINK if you want to monitor energy consumption from a blinking LED of the meter,
- DLMS if you can see
dlmslogo on the meter, - SML if you see Public Key, Server-ID, German language and no
dlmslogo, - IEC 62056-21 otherwise.
Protocols¶
IEC 62056-21¶
It is an international standard for communication with utility meters. It is the main protocol supported by the OneMeter device. Previously known as IEC 61107. The communication interface is an optical serial port on the meter (see Installation). The meter is always waiting for data request.
OneMeter device first asks for the meter identification which contains identifiers of meter manufacturer and model. Then, it asks for meter data set (list of OBIS codes and their values) which is answered on demand.
More information: OBIS codes.
SML¶
Smart Meter Language (SML) is the standard protocol for communication with German electricity meters. It is a binary encoded protocol formed by files, messages and elements. The communication interface is an optical port compliant with the IEC 62056-21. In the default mode, the meter sends a file every a couple of seconds.
Each transmission contains a file which consists of header, body and footer. The body contains a message from which meter consumption data can be extracted and formed into OBIS codes.
More information:
- Technische Richtlinie BSI TR-03109-1, SML specification version 1.04 from the Bundesamt für Sicherheit in der Informationstechnik (Federal Office for Information Security)
- Smart Message Language - read out electricity meters, SML decoding
BLINK¶
BLINK is a proprietary protocol for counting power and energy consumption based on the meter LED blinking output (so called control output / impulse output). The communication interface contains LED which blinks in tact with energy consumption.
Mostly, you will know the rapidness of power consumption of your electric installation (e.g. 1000 LED impulses per kWh). Sometimes blinks instead are related to data given to the grid, however it will rather not inform you how much data you produced.
DLMS¶
DLMS compatibility issue
We already have a working prototype of DLMS protocol compatibility. In majority of cases, the device need to obtain encryption keys in order to communicate with the meter though. Distribution System Operators (DSOs) rarely share them with users. As a result, the DLMS compatibility is still considered as not provided.
Device Language Message Specificiation (DLMS) is the global standard for smart energy metering, control and management. It specifies an object-oriented data model, an application layer protocol and media-specific communication profiles. The communication interface is an optical port compliant with IEC 62056 standard.
Each transmission requires association with the meter. A lot of times data transfer is encrypted. As a result, the device needs to be aware of encryption keys in order to handle the transmission. That keys can be obtained from the Distribution System Operators. Without this knowledge readout cannot be performed.
DLMS and its object model (COSEM - Companion Specification for Energy Metering) for virtual application description, can be used for all utilities / energy kinds, all market segments and all applications over any communication media.
More information: DLMS Overview