Thousands of perfectly good meters, PLCs and sensors sit in European plant rooms speaking Modbus RTU over RS485, waiting for someone to run a cable to them. Usually nobody does, because the cable run is the expensive part. A converter fixes this: a small box wires to the device's A and B terminals, polls its registers on a schedule, and sends the values over LoRaWAN to a gateway. The Milesight UC100 does exactly this for €45.
How a Converter Actually Works
The converter acts as the Modbus master. You configure which registers to read (total kWh at register 0x0156, say, for an Eastron meter), how often to poll, and how to pack the values into a LoRaWAN payload. From there the data follows the usual path to your platform. Writes work too: a downlink from the server can set a register, which is how remote relay switching is done.
One detail saves money at scale: RS485 is a bus. Several meters in the same cabinet can share a single UC100, each on its own Modbus address, so the per-meter cost of going wireless drops below the price of a coffee machine.
Which Converter for Which Job
| Device | Reads | Sends over | Price |
|---|---|---|---|
| Milesight UC100 | Modbus RTU over RS485 | LoRaWAN EU868 | €45 |
| Acrios ACR-CV-101L-M | Wired M-Bus (heat, water, gas meters) | LoRaWAN EU868 | €199 |
| SenseCAP Sensor Hub | Modbus RTU over RS485 | 4G cellular | €270 |
The split is simple. Modbus device plus an existing or planned LoRaWAN network: UC100. Wired M-Bus meters, common in heat and water metering: the Acrios converter, which puts a whole M-Bus loop onto LoRaWAN in one box. A site with no gateway and no plan for one: the SenseCAP hub reports over 4G instead, with the SIM cost that implies.
Check These Four Things Before Ordering
First, the register map. You need the device's Modbus documentation to know which registers hold the values you care about; without it, commissioning becomes guesswork. Second, power. The UC100 wants a local supply, and meters in the same cabinet usually have one available. Third, polling interval. LoRaWAN duty-cycle rules limit how much airtime each device may use, so polling every few minutes is realistic and polling every second is not. Fourth, device count per converter: check the spec sheet limit before planning one UC100 for a cabinet of twenty meters.
Frequently Asked Questions
Can one UC100 read several Modbus meters?
Yes. RS485 is a multi-drop bus, so meters sharing the cable each get their own Modbus address and one UC100 polls them in turn. Check the UC100 datasheet for the supported device and channel limits before planning a very large bus.
Does converting to LoRaWAN change the meter readings?
No. The converter transports register values; it does not alter them. A reading from an MID-approved meter is the same reading whether it travels over RS485 cable or LoRaWAN radio.
Can I write to a PLC through the converter, or only read?
Both. The UC100 supports LoRaWAN downlinks that write Modbus registers, which covers setpoint changes and relay commands. Keep in mind that downlink capacity on LoRaWAN is limited, so it suits occasional commands rather than continuous control.
What about wireless M-Bus meters?
The Acrios unit here handles wired M-Bus. Wireless M-Bus is a different radio protocol with its own receivers; our comparison of wireless M-Bus and LoRaWAN for water metering covers when each makes sense.
Keep the Meters, Lose the Cable Run
The hardware in your cabinets is rarely the problem; the missing link to it is. A €45 converter and a gateway you may already own turn a silent Modbus bus into live data, and the meters you paid for years ago finally report for work. If you are unsure what your installed devices can expose, send us their model numbers and we will tell you what a converter can read from them.
Putting Legacy Hardware Online?
The shopioT engineering team helps integrators map registers, pick converters, and ship them pre-configured for the network.