Meet Metron — the OnMeters module. It snaps magnetically onto the optical port of your meter — battery-powered, no wires, no electrician, no broken seals — and sends live readings to your phone over Bluetooth or to your home network over WiFi.
Get Metron See live demoMetron is just the round optical head. It clips onto the electricity meter you already have — nothing is replaced, opened or rewired.
Six parts, zero maintenance. The battery recharges over USB-C — you never open it or buy new cells.
Meter in the basement, out of Bluetooth range? Every Metron can relay readings from other units — hop by hop until they reach your phone.
Mesh relay ships as a free over-the-air firmware update.
Every Metron is a node. Together they form a self-building mesh — no router, no internet, no wiring. A reading from any meter hops across the network until it reaches your phone.
Mesh networking ships as a free over-the-air firmware update.
Put any one Metron on WiFi and it collects the entire mesh — then serves a live dashboard at onmeters.local. Open it from any computer on your network. No app, no cloud, no login.
The built-in web dashboard ships free — nothing leaves your network.
No rewiring, no electrician, no subscription. Attach the magnetic optical head and start reading in seconds.
Magnetic probe aligns with the meter's IR port. No seals broken, no warranty voided — the meter isn't modified in any way.
Use Bluetooth for quick reads on your phone, or switch to WiFi and get a live dashboard plus JSON API on your home network. Toggle by button, app, or API.
Energy import/export, tariffs T1/T2, instantaneous power, per-phase voltage and current, frequency, power factor, serial number and more.
Detects whether your meter speaks IEC 62056-21, DLMS/COSEM or SML — including automatic baud rate negotiation from 300 to 19200 bps.
Built-in MQTT with auto-discovery: your meter's sensors appear in Home Assistant automatically. Plus a clean JSON API for Node-RED, InfluxDB or your own scripts.
Reads locally, stores locally. No cloud account required — nothing leaves your network unless you send it there.
From box to first reading in under a minute.
Place the magnetic optical head on your meter's IR interface. It self-aligns.
No wires — it runs for months on a coin battery. Prefer permanent power? Just plug in a USB-C cable.
Pair over Bluetooth, or press the mode button to join your WiFi and open onmeters.local.
All OBIS registers refresh every 30 seconds. Watch usage live or pull it via the API.
No app store needed — the OnMeters web app runs in your browser and connects straight to the device.
This is what the OnMeters dashboard looks like — simulated with realistic meter data.
| OBIS | Register | Value |
|---|
One device, three protocol stacks — covering the vast majority of meters with an optical port.
Classic ASCII readout (modes A, B, C) with automatic baud switching from 300 up to 19200 bps. The workhorse protocol of European and Middle-East utility meters.
Binary HDLC framing used by modern smart meters. Metron captures push telegrams and decodes OBIS-coded registers automatically.
Smart Message Language push telegrams, standard on German-market meters (eHZ and others). Fully passive — just listen and decode.
Tested meter families by brand. As a rule: if your meter has the round optical (IR) port, Metron can read it.
The same Metron core — Main board, battery, BLE/WiFi, app and Home Assistant integration — with a sensor head for each utility.
Optical head on the meter's IR port. Full OBIS readout: energy, power, voltage, tariffs — live on your phone or network.
A pulse/dial sensor head clips over your existing water meter and counts the spinning dial — turning it into a smart meter you read remotely, leak alerts included.
A magnetic pulse head mounts externally on gas meters (no wiring near gas) and streams consumption remotely over WiFi or MQTT — same app, same dashboard.
Electricity, water and gas — one app, one dashboard, one Home Assistant device.
| Module | Metron — OnMeters optical reader |
| MCU | Main board dual-core 240 MHz, 520 KB RAM, 4 MB flash |
| Optical interface | IEC 62056-21 IR head, magnetic mount, 300–19200 bps, 7E1/8N1 |
| Connectivity | Bluetooth LE 4.2 (Nordic UART service) + WiFi 802.11 b/g/n 2.4 GHz — switchable |
| Interfaces | Web dashboard (onmeters.local), JSON REST API, BLE notifications, MQTT + Home Assistant discovery |
| Protocols | IEC 62056-21 (A/B/C), DLMS/COSEM (HDLC push), SML |
| Power | Rechargeable LIR2450 cell (months of typical BLE use), charged via USB-C — or USB-C 5 V for permanent power & WiFi mode |
| Update rate | Configurable — from every 30 s up to a few reads per day or month (battery saving with deep sleep) |
| Integrations | Home Assistant (MQTT auto-discovery), Node-RED, InfluxDB/Grafana |
If your meter has a round optical (IR) port on the front — most modern utility meters do — Metron will very likely work. It auto-detects IEC 62056-21, DLMS and SML. Contact us with your meter model if unsure.
No. The optical head attaches magnetically to the outside of the meter. Nothing is opened, no seals are broken, and the utility's meter is untouched.
Three ways: hold the mode button for 3 seconds, send the MODE=WIFI command over Bluetooth, or call /api/mode on the web API. The setting is remembered across power cycles.
No. Everything runs locally. In WiFi mode the dashboard and API live on your own network; in Bluetooth mode data goes straight to your phone.
Yes — natively. Set your MQTT broker once and every OBIS register auto-appears in Home Assistant as a sensor with the right units and device classes. The JSON API also works with a RESTful sensor.
Get in touch for pricing, availability and meter compatibility checks.
Order now info@onmeters.comProduct news, firmware updates and behind-the-scenes engineering:
Follow OnMeters on LinkedIn