Products/ EMU Professional II/ LoRa
Interface · EMU Professional II
Radio in the licence-free EU868 band, range instead of data rate, meters that transmit of their own accord. This page explains how LoRa and LoRaWAN fit together, why the duty cycle determines the timing, and how the TTN template and our decoder give you readable values without any programming of your own.
A LoRaWAN power meter, often simply called a LoRa power meter, sends its readings by radio via LoRaWAN to a gateway, and from there to a network server such as The Things Network or ChirpStack. No new cables to the meter are needed.
Basics explained: What is LoRaWAN?
| Version | Article number | Shop |
|---|---|---|
| EMU Professional II 3/100 LoRa – direct connection 100 A | P20A000LO | Shop: EMU Professional II 3/100 LoRa P20A000LO → |
| EMU Professional II 3/100 LoRa ext. antenna – direct connection 100 A | P20A000LE | Shop: EMU Professional II 3/100 LoRa ext. Antenne P20A000LE → |
| EMU Professional II 3/5 LoRa – CT connection | P21A000LO | Shop: EMU Professional II 3/5 LoRa P21A000LO → |
| EMU Professional II 3/5 LoRa ext. antenna – CT connection | P21A000LE | Shop: EMU Professional II 3/5 LoRa ext. Antenne P21A000LE → |
Order online in the EMU Metering shop.
The principle
Two terms are constantly mixed up. LoRa is the radio technique – a spread-spectrum modulation that fans a narrow signal out so widely that it is still detected below the noise. That buys range at the cost of data rate. LoRaWAN is the network protocol on top of it: gateways, network server, encryption, join procedure.
The logic differs from M-Bus or Modbus: no master polls the meter. The meter sends a small packet of its own accord at a fixed rhythm, and a gateway within radio range picks it up and forwards it to the network server. A Class A device briefly opens two receive windows after each transmission: this is the basic mode of every LoRaWAN device and the most economical. The EMU Professional II works in Class C and keeps listening between its transmissions.
In Europe this runs in the licence-free EU868 band. Licence-free does not mean rule-free: a duty cycle limit applies, restricting transmission time per device and hour. That is why LoRa is made for quarter-hour or hourly values and not for per-second values.
LoRa
The radio technique. Spread-spectrum modulation, range at the cost of data rate.
LoRaWAN
The network protocol: gateways, network server, keys, join.
Spreading factor
SF7 to SF12. Higher means further and more robust, but slower and with more transmission time.
Duty cycle
Statutory limit on transmission time per device in the licence-free band.
Class A
The device transmits, then two short receive windows. The most economical mode.
OTAA
Joining over the air with DevEUI, JoinEUI and AppKey. The recommended route.
ABP
Permanently programmed session keys. Simpler, but less secure.
Payload
The useful data of the packet – compactly packed bytes, not readable text.
Data path
Whether with your own network server or straight into Joulio-Web: the meter joins via OTAA, and all readings travel end-to-end encrypted. This applies to the EMU Professional II LoRa as well as to the Helvatron H2O and DELTA III meters. The gateways only forward.
Integration
What arrives at the network server is at first a short block of bytes. To turn that into “active energy import, tariff 1, 128,431 kWh” you need a payload decoder: a small piece of code that takes the bytes apart according to the device’s payload structure.
This is exactly where LoRa projects most often fail – not on the radio link, but because the decoder was written by hand and never documented. That is why we provide it ready-made.
In the TTN network the EMU Professional II LoRa is directly available as a template. Create the device, choose the template, enter the keys – the decoder comes with it. In the most common case, that is all there is to it.
For integration into other systems the decoder is on GitHub. It comes with two tools that run straight in the browser: a payload decoder to check a received packet, and a payload generator to create test packets before the first meter is installed. Both save troubleshooting on site.
GITLoRa decoderemuag/professional_II_lora WEBPayload decoderCheck a received packet WEBPayload generatorCreate test packets
With the payload generator the whole chain from the network server to the target system can be built and checked before a single meter hangs in the shaft. That moves troubleshooting from the basement to the desk.
Radio planning
A higher spreading factor brings range and robustness, but lengthens transmission time and therefore uses up more of the permitted duty cycle. Meters in the basement often end up at SF11 or SF12, meters with line of sight at SF7.
Reinforced concrete, soil and metal cabinet doors weaken the signal more than any distance figure suggests. A meter 30 m away in the basement is harder to reach than one 2 km away with a clear view of the gateway.
A test device at the planned installation point says more than any calculation. For distributed properties a walk-through with measurements pays off before gateways are permanently installed.
Where it fits
Documents
This page explains the principle. Register lists, telegram structure, terminal assignment and the exact parameters of each version are in the interface manual.
PDFLoRa interface manual1490 · payload structure · English GITLoRa decoderemuag/professional_II_lora GITPayload generatorSource on GitHub WEBPayload decoderRuns in the browser WEBPayload generatorRuns in the browser PDFEMU Professional II data sheet1441 · English
Frequently asked questions
Yes. The EMU Professional II LoRa is approved under MID (module B+D). The values it sends come from its load profile memory and carry the timestamp of the entry.
LoRa is the radio technique – a spread-spectrum modulation that trades data rate for range. LoRaWAN is the network protocol on top of it, with gateways, a network server, encryption and a join procedure. In practice you need both.
Yes. In the TTN network the EMU Professional II LoRa is directly available as a template. Create the device, choose the template, enter the keys – the payload decoder comes with it.
Through the decoder we provide on GitHub. There is also a payload decoder and a payload generator as web tools: with the decoder you check a received packet, with the generator you create test packets to build the chain before the first meter is installed.
At a fixed rhythm, not on demand. The timing follows the duty cycle in the licence-free EU868 band, which limits transmission time per device and hour. That makes LoRa suitable for quarter-hour and hourly values, not for per-second values or control tasks.
That depends on the location, not on a number in a data sheet. Reinforced concrete, soil and metal cabinet doors weaken the signal far more than distance does. A meter 30 m away in the basement can be harder to reach than one 2 km away with line of sight. A measurement at the planned installation point beats any calculation.
OTAA, joining over the air with DevEUI, JoinEUI and AppKey, is the recommended route: the session keys are negotiated at join time. ABP works with permanently programmed keys – simpler to set up, but less secure and more awkward when a meter is replaced.
Send us the number of measuring points, the distances and the target system. We will tell you which version makes sense – and when another interface would be the better choice.
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