DLMS/COSEM overview

DLMS stands for Device Language Message Specification.

The objective of DLMS is to provide an interoperable environment for structured modeling and meter data exchange. DLMS supports applications such as remote meter reading, remote control, and value-added services for metering any kind of energy, such as electricity, water, gas or heat.

It is an international standard published as IEC 62056.

COSEM stands for Companion Specification for Energy Metering. It is an interface model for communicating with energy metering equipment, providing a view of the functionality available through the communications interfaces. The model uses an object-oriented approach.

The COSEM model allows for a manufacturer-independent and controlled method to identify, retrieve and interpret the information held in any meter.

Key terms

Term Description

Client (master)

The workstation running software. 

In this implementation, only the Client can initiate requests.

Server (slave)

The meter.

Logical device

A logical device is a container for COSEM objects. 

In this implementation, each ION meter running the DLMS protocol contains a single logical device.


A collection of attributes and their methods.


A value that describes the data.

OBIS (Object Identification System)

OBIS allows for unique identification of each of the many data items used in the energy metering equipment.


An operation performed on attributes, e.g., the SET method allows you to time sync the meter (GET means read, and SET means write).

COSEM interface

By using the COSEM interface specifications, data collection systems and metering equipment from different vendors can exchange data.

This interoperability is accomplished through object modeling.

The information of an object is organized in attributes. The attributes represent the characteristics of an object by means of attribute values. The value of an attribute may affect the behavior of an object. An object may offer a number of methods to either examine or modify the values of the attributes.

Objects that share common characteristics are generalized as an interface class with a class_id. Within a specific class, the common characteristics (attributes and methods) are described once for all objects. Each instance of an interface class is called a COSEM object.

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