Wireless MBus Overview and Diagnosis

What wireless MBus is

Wireless MBus (wMBus) is the radio version of MBus. Instead of a cable, the meter sends short messages, called telegrams, over radio, usually on the 868MHz band, to a receiver or gateway. It is widely used for battery powered meters where running a cable is not practical.

How wireless MBus works

• The meter wakes at set intervals and sends a telegram in a radio mode, such as T1 or C1.
• The telegram is usually encrypted with an AES key, so the receiver needs the same key to read it.
• A receiver or gateway in range collects the telegrams and passes them on to the platform, over a SIM or broadband connection.
• Range depends on walls, floors and metal in the building, so the position of the receiver matters.

For the full detail, read Understanding Wireless MBus for Smart Metering.

Where issues usually lie

• The meter radio is disabled or the battery is flat.
• The meter radio mode does not match the receiver mode.
• The AES key is missing or wrong, so the telegram is heard but cannot be read.
• The signal is weak or blocked.
• The receiver is offline or its connection has failed.

Diagnosis and quick approaches

Use this guide when a wireless MBus meter is not being read, or is read only some of the time. Work through the sections in order. For background on modes and encryption, read Understanding Wireless MBus for Smart Metering.

Not sure which guide you need? Start at Meters Not Reading or Poor Signal: Where to Start.

Before you start: collect the facts

• Meter manufacturer, model and the full meter ID (serial number).
• The radio mode the meter uses (for example T1 or C1) and the mode the receiver is set to.
• Whether one meter, a group of meters or every meter is missing.
• The last time a telegram was received and its signal strength.
• Whether anything changed: a battery swap, a receiver replacement, a firmware update or building works.

Good to know: If every meter is missing, check the receiver and its connection first. If only one meter is missing, check the meter, its radio and its position.

1. No meters are being received at all

1. Check the gateway or receiver has power and is showing normal status lights. Compare with the manufacturer documentation.
2. Check the gateway has a working connection to the platform. For an Elvaco Edge or CMe2100 this is the SIM card fitted in the unit, so check it is seated, active and has mobile signal. Only the CMe3100 uses Ethernet. The LED tables are in Wired MBus Overview and Diagnosis. If the gateway is still online through its SIM or network connection, try to fix it remotely before a site visit: the Elvaco CMe2100 can be configured, updated and rebooted by SMS or HTTP, the CMe3100 can be reached through its built in web interface, and the ZENNER B.One Gateway and the Elvaco Edge can be configured and updated remotely.
3. If you use a CMeX50 receiver with a CMe gateway, check the CMeX50 is linked to the gateway and that its meters and keys are loaded.
4. Check the radio mode set on the receiver matches the meters. A receiver set to C1 will not hear T1 meters.
5. Check the receiver antenna is connected, undamaged and not inside a closed metal cabinet. Use a Sycous wireless MBus antenna or GSM antenna on a lead if the unit is in a metal enclosure.
6. Check the receiver is not filtering out the meters, for example a list of meter IDs that is empty or wrong.
7. Reboot the receiver and watch for telegrams to arrive. Note the time.

2. One meter is not being received

1. Check the meter display. If it is blank, the battery may be flat or the meter may be in a storage mode. Check the meter manual. For a ZENNER C5, see Waking a Zenner C5 from Sleep Mode and its error code 800 for a wireless interface fault in Zenner C5 Error Codes.
2. Check the radio is enabled. Many wMBus meters ship with the radio off to save battery and need it activated by a button press or a configuration tool.
3. Check the meter radio mode and interval. A meter set to transmit every few hours will look dead if you only watch for a few minutes.
4. Check the meter ID on the receiver or platform against the meter label. A single wrong digit means the telegram is ignored.
5. Check the encryption key. If the receiver sees the meter signal but no readings, the key is probably wrong or missing.
6. Check the position. Take a handheld wMBus receiver or the receiver itself close to the meter. If the meter is received there, the original position has a range problem.

Warning: Do not leave a battery powered wMBus meter transmitting at a fast test interval. It will drain the battery far sooner than its design life. Return it to its normal interval when testing is finished.

3. Meters are received, but only some of the time

1. Check the signal strength. If it is weaker than about minus 105 dBm, the link has no margin.
2. Move or raise the receiver. A central, high position with clear sight of the riser works best.
3. Move the receiver away from metal cabinets, lift shafts and other radio equipment.
4. Check the antenna type. An external antenna on a short cable normally outperforms a built in one in a plant room.
5. Add a Sycous Wireless MBus Repeater between the meters and the receiver if the layout will not allow a better position. It supports T and C modes.
6. Check for new obstructions. A closed riser door, new metalwork or building works can change a link that used to work.
7. Check for many meters transmitting in the same mode at once. Collisions can lose telegrams, especially in dense blocks with fast intervals.

4. Readings arrive but look wrong

1. Check the meter display against the latest reading on the platform. If they differ, note both with times.
2. Check units and scaling. A heat meter reporting in MWh against one reporting in kWh will look a thousand times out.
3. Check the parser matches the meter model and firmware. A parser that does not know a telegram will drop fields.
4. Check for a duplicate meter ID. Two meters with the same ID will overwrite each other.
5. Check whether the meter was replaced. The platform needs the new meter ID and key.

For practical fixes to weak signal, see Improving Poor Radio Signal at a Site.

5. When to call for support

Call for support if the receiver is online, the mode matches, the key and ID are correct, the signal is strong and the meter is still not read. At that point the meter manufacturer needs to check the radio or firmware.

Frequently asked questions

Why is my wireless MBus meter not reporting?

The most common reasons are a disabled radio, a flat battery, a mode mismatch between meter and receiver, a missing or wrong encryption key, and a receiver that is too far away or screened by metal.

How do I know if the meter or the receiver is at fault?

Check whether other meters near the same receiver are being received. If they are, the receiver is working and the fault is with the meter or its position.

What does it mean when I get a signal but no data?

The receiver heard the radio telegram but could not decode it. Check the encryption key first, then the telegram type and parser.

How far can a wireless MBus meter transmit?

In open air it can be hundreds of metres. In a building, the number of walls and floors matters far more than the distance, and a few floors of concrete can stop the signal altogether.

How long does a wireless MBus battery last?

Many are designed for ten years or more, but fast transmit intervals, cold plant rooms and repeated testing all shorten that.

Need a hand on site? Contact Sycous at info@sycous.com and have the details from the checklist above ready.