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Knowledge base — metering technology and communication

Four decades of metering expertise gathered in one place. Here we explain how the technologies work, what the concepts mean and why it matters when you choose a solution.

How, what and why
Measurement principles

How the meters work

No single metering technology suits every application. Here are the principles behind the technologies in our range — and when each one is the right choice.

Multi-jet meter

WhatMechanical velocity meter in which the water drives an impeller whose rotational speed is proportional to the flow.
HowThe flow is directed through several channels (jets) around the impeller, which distributes the load evenly across the bearings and gives a longer service life than single-jet meters. The register totalises the revolutions into volume.
WhyProven, cost-effective and robust technology for domestic water in apartments and houses. With modern register add-ons (pulse, M-Bus, wM-Bus, LoRaWAN), even the mechanical meter becomes part of smart metering.

Woltmann meter

WhatMechanical bulk meter in which an axial turbine rotates in the direction of flow — for large flows in distribution networks and industry.
HowThe turbine's rotation is geared down mechanically to the register. The design gives low pressure loss even at high flows and is available in sizes up to DN 300 and beyond.
WhyThe right choice for main water metering, distribution monitoring and billing of large offtakes — where multi-jet meters are too small.

Ultrasonic meter (static)

WhatA meter with no moving parts at all that measures flow using sound pulses.
HowTwo transducers send ultrasonic pulses alternately with and against the direction of flow (the transit-time principle). The time difference between the pulses is directly proportional to the flow velocity. No mechanics to wear out, and no effect from particles under normal conditions.
WhyHigh accuracy even at very low flows (high R-values, up to R1000), long service life, insensitivity to wear and often no need for straight pipe runs — which is why static technology is taking over in both IMD and distribution metering.

Clamp-on ultrasonic

WhatUltrasonic metering with transducers mounted on the outside of the pipe.
HowThe transducers send the sound pulses through the pipe wall. No drilling, no contact with the medium, no process interruption — and the meter can be moved between measuring points.
WhyPerfect for verification metering, fault-finding, temporary monitoring and installations where the process must not be stopped. From DN 10 to DN 10,000.

Electromagnetic meter (inductive)

WhatFlow meter that uses Faraday's law of induction: a conductive liquid moving through a magnetic field induces a voltage proportional to its velocity.
HowMagnetic coils around the measuring tube create the field, and electrodes in the pipe wall measure the voltage. A free, unobstructed bore gives negligible pressure loss.
WhyThe standard choice for water and wastewater applications and process industries with conductive liquids — insensitive to particles, sludge and viscosity. Requires a conductive medium (does not work for oil or pure deionised water).

Coriolis meter

WhatMeasures mass flow directly — not volume.
HowVibrations in the measuring tubes are affected by the medium's mass flow (the Coriolis force), and the resulting phase shift is measured. It also provides density and temperature simultaneously.
WhyWhen mass is what counts: dosing, recipe handling, energy carriers and media whose density varies. Very high accuracy — which is why our laboratory uses mass-flow references with ±0.15 %.

Vortex meter

WhatMeasures flow via vortex shedding behind a bluff body placed in the flow.
HowThe frequency of the vortices (the Kármán vortex street) is proportional to the flow velocity and is detected by a sensor.
WhyA robust choice for steam and gas, where other technologies struggle — no moving parts and a wide measuring range.

Radar level measurement

WhatNon-contact level measurement using radar pulses.
HowThe meter transmits microwave pulses towards the surface and measures the travel time of the echo. A narrow beam angle (such as SPECTRA's 8°) reduces interference from walls and obstacles, and smart filtering removes false echoes.
WhyInsensitive to weather, dirt, foam and temperature — which is why it is the first choice for level monitoring in sewers, stormwater, reservoirs and flood monitoring. See SPECTRA.

Weighing as a reference method

WhatThe most fundamental measurement principle: volume is determined by weighing the water.
HowWater of known temperature and density is collected and weighed on traceably calibrated scales. The mass is then converted to volume.
WhyThis is how our accredited laboratory realises its reference standards — weighing provides the unbroken chain of traceability to national standards, with measurement uncertainty down to ±0.2–0.3 %.
Concepts

R-value, MID and accuracy

What does the R-value mean?

The R-value (dynamic range, or turndown) is the ratio between the meter's permanent flow Q3 and its minimum flow Q1 as defined by the MID. A meter rated R800 therefore measures correctly all the way down to 1/800 of its nominal flow. A high R-value means that even small draws — a dripping tap, a leaking toilet — are registered and billed correctly. It is the difference between detecting a leak on the very first invoice and never seeing it at all.

What is the MID?

The Measuring Instruments Directive (2004/22/EC, now 2014/32/EU) is the EU framework for measuring instruments used for billing. A MID-approved meter has undergone type testing and production control by notified bodies. Swedac oversees and accredits the bodies that verify this. For the billing of water and energy, MID approval is in practice a requirement — without it you risk legality, accuracy and the trust of residents alike. Technical standards such as EN 1434 (heat meters) and EN 14154 (water meters) govern design and testing.

Accuracy is perishable

A meter's accuracy at delivery says nothing about how it reads after ten years in service. Wear, deposits and ageing electronics all take their toll. That is why there are rules on recurring inspection (STAFS 2007:2) with defined in-service intervals — and why we recommend recurring, well-planned calibration for industrial process meters. Read more about accredited inspection & calibration.

Communication

How the readings get home

The choice of communication technology determines cost, battery life and how often you receive data. Here are the technologies — and when they fit.

Pulse

WhatThe simplest signal: the meter closes a contact for each unit of volume consumed, e.g. one pulse per litre.
HowA two-wire line to a pulse counter, logger or substation. One-way — the receiver must keep the running total itself.
WhyCheap and universal — but with no error checking: lost pulses go undetected. Good as a local supplement, less suitable as the sole reading path for billing.

M-Bus (wired)

WhatMeter-Bus per EN 13757 — the industry standard for wired meter reading.
HowA two-wire bus in which a central unit (master) powers and reads up to hundreds of meters (slaves). The meter transmits the complete register reading with ID, timestamp and status.
WhyHighly reliable in buildings: no battery concerns, full error checking, and the actual register reading instead of counted pulses. It requires cabling — the obvious choice for new construction and major renovation.

Wireless M-Bus / OMS

WhatThe radio version of M-Bus at 868 MHz, standardised through the Open Metering System (OMS).
HowThe meter transmits encrypted telegrams at regular intervals. Reading is done either mobile (walk-by/drive-by) or via fixed receivers in the building.
WhyNo cabling, and an open standard with broad brand coverage — the backbone of most IMD installations. Range up to a few hundred metres depending on the environment.

LoRaWAN

WhatLong-range radio (Long Range WAN) in the licence-free band, built for battery-powered sensors.
HowThe meters transmit to gateways with a range of up to several kilometres. The network can be your own (your own gateways) or an operator's. Dual-mode meters combine LoRaWAN with wM-Bus as a fallback.
WhyWhen the measuring points are dispersed — community associations, area networks, municipal facilities — LoRaWAN provides remote reading with no subscription cost per meter and many years of battery life.

NB-IoT and Cat-M1

WhatCellular IoT communication over the operators' licensed frequencies.
HowThe meter has its own SIM and transmits directly over the mobile network — no dedicated infrastructure needed. NB-IoT is optimised for small volumes of data and offers very good indoor and underground coverage.
WhyThe right choice for isolated measuring points far from other infrastructure: fire hydrants, wells, reservoirs. SPECTRA and HYDRANTIQ use Cat-M1/NB-IoT for exactly this.

NFC

WhatNear-field communication for configuration and reading at arm's length.
HowA technician holds a phone or reader against the meter to read the register, run diagnostics and change settings — without opening the meter.
WhyFast commissioning and fault-finding in the field, as a complement to remote reading.

MQTT and API

WhatThe integration layer on top of the radio technology: how the data reaches your monitoring or business system.
HowMQTT is a lightweight publish/subscribe protocol that streams readings in real time to any receiver; REST APIs retrieve data on demand. HYDRANTIQ can, for example, send MQTT straight into your control system.
WhyYou should never be locked into a single collection system — open interfaces mean OneViewer, your SCADA or your property manager can all consume the same data.

How do you choose?

Dense building, new constructionWired M-Bus — most reliable, no battery management
Existing building, IMDwM-Bus/OMS — no cabling, walk-by or fixed receivers
Dispersed area, community associationLoRaWAN — kilometre range, your own gateways, long battery life
Isolated measuring point, infrastructureNB-IoT/Cat-M1 — the mobile network is already in place
Upstream integrationMQTT or API — real-time data into your own systems

Not sure? We size and select the technology for you — contact us or read about meter-reading collection with OneSystem.

Calibration

Why calibrate — and what the words mean

Calibration and adjustment are different things

The misconception that a calibrated meter reads "correctly" is common. A calibration is only a comparison against a good reference — the result is used to add or subtract the deviation after measurement. If you want to change what the meter displays, that is called adjustment. The sequence is: an initial calibration that indicates whether adjustment is warranted, then adjustment, and finally the concluding calibration. There is no such thing as a meter that reads correctly — there are only competent users who know how large the deviation is.

Traceability — the unbroken chain

A calibration result is only worth something if the reference is itself calibrated against a better reference — all the way up to national or international standards. This is called traceability, and ISO/IEC 17025 requires an unbroken chain with a stated measurement uncertainty at every link. That is what separates an accredited calibration certificate from an internal report.

When did you last calibrate your meters?

A meter that is not calibrated regularly can lead to faulty decisions and financial losses. With recurring, well-planned calibration, your future decisions rest on the right information — and you gain confidence and credibility towards your own customers. Book a slot: that way you can plan when the meters can be spared, and you avoid long waiting times. Normal lead time is up to four weeks.

To accredited inspection & calibration