Mounting the module

  1. Mount CMeX20W on a DIN-rail on the left side of, and as close as possible to, the meter.

    There should be a maximum of 3 mm between the devices.

  2. Use the metallic clip on the bottom to mount and demount the unit from the DIN-rail.

    For safety reasons, a DIN-rail enclosure must cover the terminals.


Avoid mounting the product in a metaI cabinet. It will reduce the ability of the product to connect to a master.


lf the product is installed in a metaI cabinet, an externaI antenna for wireless M-Bus, should be used.

Connecting the power supply


The installation must be performed by a qualified electrician or another professional with the required knowledge.


The power supply must be protected with a 10 A circuit breaker of characteristics C or slow blow fuse.

  1. Connect main supply to screw terminal for power supply N and power supply L. Main supply voltage should be in the range of 220-240 VAC, 50 Hz.

  2. Connect the power to a clearly marked and easily accessible switch to make sure the product can be switched off during service work.

Communication with ABB electricity meter

IR communication

CMeX20W starts searching for ABB electricity meter as soon as the supply voltage is connected.

For CMeX20W to be able to find ABB electricity meters, it must be configured correctly (see the ABB meter's manual for complete information). The optic interface must be activated and the communication speed should not be over 9600 baud.

The CMeX20W can then automatically sense which baud rate the ABB meter is using and adapt after that.

When CMeX20W cannot establish any contact with the ABB meter, the LED will light up red. As soon as it establishes contact with the ABB meter it will light up green or yellow (depending on the encryption).

CMeX20W can handle an IR communication of maximum 9600 baud. The ABB meter can be set to a higher speed, but then the CMeX20W will not find the meter.

Wireless M-Bus messages

The radio will start when CMeX20W has a functioning IR communication with the ABB meter. The radio will send Wireless M-Bus messages with meter values in Wireless M-Bus mode T1.

Activating the module

Selection of unencrypted or encrypted mode is made when the product is activated during installation. Advise your project manager which operation mode is used in your project.

Switch between modes

Press and hold button SW1 to switch between encrypted and unencrypted mode.

Unencrypted mode

Meter data is sent unencrypted and no encryption key is needed to decrypt the data.

The LED will turn green when unencrypted mode is activated.


When the LED turns off (in about 500 ms), data is sent via wireless M-Bus. This occurs every 16 seconds.

Encrypted mode

The meter data is sent encrypted and an encryption key is needed to decrypt data. The information is encrypted using a 128 bit AES-key. When entering the key, you connect it to ABB's secondary address, so it's important to know which CMeX20W belongs to which ABB meter.

The LED will turn green when encrypted mode is activated.


When the LED turns off (in about 500 ms), data is sent via wireless M-Bus. This occurs every 16 seconds.

The ABB electricity meter's telegram is too large to fit in the encrypted wireless telegram. The telegram is sent wirelessly, but up to nine byte may have been truncated at the end of the meter's telegram.

The LED will flash yellow when the telegram is too large.


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