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Mobius : a low cost current sensor with world leading metrology

Mobius - at the heart of your next smart electricity meter

The Mobius current sensor is at the heart of the latest generation of smart electricity meters, providing an energy measurement solution that is simple to integrate, and acts as a highly cost-effective platform that simplifies the design process and reduces the time to market for new generations of product.

Mobius has more than 1 billion service hours in award-winning meters in the US and is now being integrated into designs for metering products worldwide.

Sentec technology is now included in almost 8 million meters installed in the USA today, the vast majority of which are smart electricity meters.

Opening up the smart meter market

As the market for smart meters expands, unprecedented pressures are being placed on the design process. Competition is centred around the application and system functionality and the services offered, and companies bringing this fresh perspective to the market don’t want to be distracted by the underlying metrology performance of the meter – they want proven, accurate technology that is simple to integrate with their networking and communication technology, and easy to put into volume manufacture with little or no tooling and no risk of type approval delay.

Key Benefits

Its unique design features means that:

easily adapted to fit with most standard configurations of terminals, sockets, and disconnect switches,
minimise the mechanical design complexity and part count,
simplify the assembly process
exceptionally high accuracy and low cost - suitable for a wide range of meter types,
design investment can be recouped across many products
sensor is made as part of a pcb, so no supply chain issues

Unlike competing component solutions, manufacturers using Mobius have no supply chain issues, because the sensor is made as an integral part of a completely standard printed circuit board. Licensees enjoy protection over their competitors thanks to Mobius’s strong international patent portfolio.

Mobius is, therefore, an ideal solution for any manufacturer seeking to develop a new range of electricity metering products to address the requirements of the highly competitive smart metering market.

Faster development, lower cost, better functionality

The measurement of electric current and power is fundamental to energy measurement and billing systems and Mobius offers a technological breakthrough in bringing high-performance low-cost sensors to smart meters in high-volume cost-sensitive markets.Manufacturers using Mobius benefit from its inherently superior performance and design characteristics:

Patented - granted international patent protection
Accurate - meets the most stringent ANSI and IEC class 0.2% accuracy requirements
High current - ideally suited to higher-current applications, up to 320A in service today
Stability – long term calibration accuracy, ~zero temperature coefficient
Linearity – easy and quick calibration, class-leading accuracy well beyond standards
Air cored – no permeable magnetic core to saturate or magnetise
Novel structure – provides total immunity from DC magnetic tampering
Full isolation – suitable for 2, 3 or 4-wire services
Low cost – sensor is formed in the tracks of a standard PCB over a small board area
No supply chain issues – can be fabricated by any good quality PCB vendor
Integrates directly with many vendors’ metrology chips and SOC’s
Mechanical configuration of conductors easily adapted to fit any socket, terminal or switch layout

Compete effectively in the smart meter market

Mobius current sensors offer meter manufacturers an opportunity to produce a superior design more rapidly and at a lower cost, and to do so across a full range of metering products. In a competitive market where product innovation is key and where design times are rapidly being reduced, manufacturers who can respond rapidly to new market requirements will have a significant advantage in their ability to win large tenders.

Designs based around Mobius have low technical risk, exhibiting excellent performance from very early in the design process, significantly reducing the risk in the product development cycle. The sensor itself requires no tooling, as it is simply part of the printed circuit board, whilst the conductors are typically planar, formed from stamped copper sheet, minimising the tooling costs and timescales. The final assembly process is well suited to a flexible manufacturing approach using contract manufacturing, allowing rapid ramping of the process to high volumes. The combination of these features can significantly shorten the overall time to market and fulfilment of customer orders.

How it works

Mobius sensors achieve their outstanding performance as a direct consequence of one of the most basic laws of electromagnetism, Faraday’s Law of Induction: “The induced electromotive force or EMF in any closed circuit is equal to the time rate of change of the magnetic flux through the circuit”. Current passing through a primary conductor produces magnetic flux, which passes through a secondary circuit coil arrangement (the sensor), formed as tracks in a printed circuit board, to create a voltage which is directly proportional to the rate of change of current in the primary conductor.

The key to the design is to make sure that the sensor couples magnetic flux only from the primary conductor, with high stability, and not from other nearby conductors or externally generated fields. Mobius sensor coils are planar, fabricated using the inherent geometrical precision of standard circuit board processes, and incorporating the patented features that deliver the desired performance.

Supporting documentation

Mobius sensors are incorporated into millions of electricity meters in North America, which is the most demanding market in the world, requiring 0.2% accuracy even for standard residential applications. This means it is easily able to meet the accuracy requirements in all other territories.

To assist with the design and integration process, Sentec sell evaluation kits, which come with full schematic and bill of materials. For the most rapid product integration, from 2010, Sentec plan to have available self-contained Mobius metrology modules, simplifying further the task of turning a communications device into a complete meter product.

Commercial proposition

Mobius is protected by world-wide patents, so in order to enjoy the benefits of the technology, manufacturers must either buy complete sensors from Sentec Ltd, or obtain a licence to use the sensor technology for their specific products and territories. For electricity metering applications, Mobius is now only available outside of North America and ANSI metering standards. Please contact Sentec for more specific details on the rights and territories that are still available.

Sentec’s world-class product development team can work with licensees or sensor customers on all aspects of the product development, including mechanical design, firmware, electronics, integration with existing systems, design for manufacture/test, tooling, contract manufacture support, manufacturing systems and databases, compliance, calibration and testing.