Think of a connected system as five parts: meter → interface/module → network or gateway → software → billing, dashboard or control system. A quotation should identify who supplies and maintains each part.
Compare the main options
| Interface or network | Useful for | Advantages | Limitations and purchase checks |
|---|---|---|---|
| Local visual register | Occasional manual reads, small installations | Simple and independent of a communications network | Reading access, labour and transcription errors; usually limited history |
| Pulse output | Retrofitting a logger, counter or building input | Simple way to transfer increments of volume | Exact L/pulse, pulse width, contact type and logger power; missed counts can cause drift |
| Absolute encoder/digital register output | Sending a meter's actual accumulated reading | Can avoid relying solely on externally counted pulses | Protocol, reader compatibility, reading resolution and cable limits |
| 4–20 mA | Continuous flow signal to a PLC/process system | Familiar analog input; straightforward scaled process value | Usually a rate signal, not an independent cumulative-volume record; scaling and loop power must match |
| HART over 4–20 mA | Industrial instruments and asset diagnostics | Digital information alongside a compatible analog loop | Requires HART-capable meter and host; a plain analog input does not read HART data |
| BACnet, native or through a gateway | Building automation | Can fit an existing building-system interface | Confirm BACnet variant, supported objects, units and gateway mapping; do not infer it from BMS wording |
| Modbus RTU over RS485 | BMS, PLC and industrial monitoring | Multiple digital values on a wired network | Register map, data types, scaling, byte/word order, serial settings and wiring design |
| Wired M-Bus | Building consumption metering | A meter-reading bus with many compatible products | Master capacity, device loading, supported data records and actual interoperability |
| Wireless M-Bus / OMS | Walk-by or fixed-network meter reading | Avoids a cable to every meter | Radio mode, frequency, security profile, keys and gateway/payload compatibility |
| LoRaWAN | Campuses, sites and distributed low-data telemetry | Low-power radio with private or public network options | Site coverage, gateway/backhaul, network server, payload decoder, key ownership and reporting limits |
| NB-IoT / LTE-M / other cellular | Dispersed locations with suitable operator coverage | Can connect through an operator network without an on-site LoRaWAN gateway | Exact radio technology/bands, SIM charges, coverage in pits, battery assumptions and lifecycle support |
| Proprietary RF / walk-by / drive-by | Operator-managed reading rounds | May suit an established reading system | Receiver/software dependence, actual read frequency and supplier lock-in |
| Ethernet, Wi-Fi or Bluetooth | Powered equipment, gateway uplinks or local commissioning | Useful where the supporting infrastructure fits | Do not assume a meter has a direct internet connection; Bluetooth may be commissioning-only |
HART adds digital communication to a compatible 4–20 mA loop. BACnet serves building automation; it is a separate protocol choice. FieldComm Group HART, BACnet International
The comparisons are practical procurement guidance. M-Bus and wireless M-Bus are distinct interfaces within the EN13757 family; OMS adds system specifications. M-Bus overview
RS485 specifies an electrical interface; it does not by itself promise Modbus or identify any register. For a working integration, obtain the meter manufacturer's map and use the appropriate serial implementation guidance. Modbus Organization specifications
LoRaWAN supports low-power utility networks, but a matching radio label alone does not guarantee that application data will decode correctly. LoRa Alliance utilities overview
Cellular options depend on the particular technology and operator network, not just a generic “GSM” or “4G” description. GSMA utility IoT overview
Pulse output: check the complete counting chain
Specify litres per pulse, electrical type, maximum voltage/current, pulse width and maximum frequency. Match these to the logger input and its debounce settings. Document the starting register reading and how counts survive a logger restart.
If a meter emits one pulse per 10 litres, one pulse represents 0.01 m³. At 5 L/min it emits, on average, one pulse every two minutes. A quiet one-minute interval therefore does not prove zero water use. These are calculated examples, not performance claims for a particular meter.
A reed contact, open-collector output and actively driven output need different electrical treatment. “Pulse-ready” may mean a pickup can be added later. Ask whether the sensor, lead and compatible counter are included.
Modbus and BMS: ask for proof of interoperability
Request a sample integration showing flow, totalizer, units, faults and meter identity. Confirm register addressing, integer/float format, scaling, byte/word order, baud rate, parity and stop bits. Record how reverse totals, resets and overflows are represented.
The BMS acronym means building management system; it is not a communications protocol. BACnet, Modbus, M-Bus and pulse are different interfaces, sometimes joined through a gateway. Price the gateway and engineering work where required.
Do not expose a legacy serial/control interface directly to the public internet. Specify authenticated access through the supported system architecture. Modbus Security is a separate TLS-based protocol; its existence does not mean every Modbus device implements it. Modbus specifications and security
AMR, AMI and “real time”
AMR commonly describes automated reading, including walk-by and drive-by collection. AMI commonly describes networked metering infrastructure with recurring remote data collection and management. Vendors use the labels differently; buy the capabilities you need. Kamstrup remote reading options
Ask separately for the measurement interval, logging interval, transmission interval and alarm-delivery delay. A device may measure frequently, store hourly values and upload once daily. That is not a continuously live dashboard.
If a network fails, will the meter keep measuring? How long can it store data? Will it backfill missing records? Can a remote reading be reconciled with the local register after recovery? Require explicit answers.
Battery life and remote control
Ask suppliers to state battery-life assumptions: measurement rate, radio conditions, retries, upload frequency, temperature, display use and valve operations. Compare quotations using the same operating profile. A claimed ten years at one upload a day cannot be assumed at one upload a minute.
An integrated shutoff valve adds a control function. Specify valve pressure loss, closing behavior, permissions, logs and what happens during power or communications failure. Do not assume that every remote meter can close a valve, or that a telemetry network provides a guaranteed emergency response time.