Mounting the product

  • Mount the sensor on the wall using the holes on the sensor rear cover. Avoid using the holes that are crossed out in the following image.

    Mounting instruction

    Mounting instruction


Don’t mount the product near supplementary heat sources, such as kitchen stoves or in direct sunlight.


Mount the product at least 1.5 meters above the floor and at least 1 meter from nearest radiator.


Don’t mount the product on an external wall or near a door. If mounted over a conduit pipe, make sure that the pipe is filled to prevent air flow.

Demounting the sensor

  • Carefully insert the end of a screwdriver in the upper part of one of the enclosure top holes, according to the following image.


    Demounting instruction

Activating the sensor

CMa12w is delivered in inactive mode, which means that the product is not performing any tasks in order to conserve battery life. The product needs to be activated in order to start transmitting data. CMa12w can be activated in unencrypted mode (all data is transmitted unencrypted) or encrypted mode (all data is transmitted encrypted).


Verify that the device has been activated by pushing SW1. If the product has been activated in encrypted mode, the LED light (2) will flash five times. If activated in unencrypted mode, it will flash once.

Activate the sensor in unencrypted mode

  1. Press and hold push button SW1 for 6-10 seconds until the LED lights starts to flash quickly.

  2. Release push button SW1.

  3. The product will transmit unencrypted wireless M-Bus telegrams (SND_NR) in C1 mode once every 180th second.

Activate the sensor in encrypted mode

  1. Press and hold SW1 for at least 13 seconds until the LED light starts to flash slowly.

  2. Release push button SW1.

  3. The product will transmit encrypted wireless M-Bus telegrams (SND_NR) in C1 mode including sensor data and product/battery status once every 180th second.

The encryption is performed by a 128-bit AES algorithm.


The encryption key must be known to the receiving system in order to decrypt incoming data. The 128 bit AES key can be provided by Elvaco on demand.


When the product has been activated, encryption mode cannot be changed.


Encrypted/unencrypted mode activation

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