Electricity Meters

Solid state electricity meters are evolving and different solutions/architectures are today used in the metering markets around the world. These products are responsible for energy and power measurement and data display. They may require battery operation with real time clock (RTC) running when the product is not connected to a power main, to support features like "read without power".

The basic e-meter is a direct replacement for the traditional mechanical meter. This product still needs to be read manually, and is generally based on an 8-bit microcontroller, such as Atmel® AVR microcontrollers
Automatic Meter Reading (AMR) meters provide one-way communication, enabling electricity providers to read the meter automatically and remotely using different communication solutions including RF wireless, Power Line Carrier, and GPRS
Smart Meters employ an Advanced Metering Infrastructure (AMI) architecture, enabling two way communication back to the utility company, as well as variable tariffs, outage monitoring, prepayment, and remote disconnect. Smart Meters can also communicate directly with other meters, and with an in-house display unit
The most advanced metering system is a Smart Grid implementation, which requires a full AMI deployment of Smart Meters and offers improved monitoring, communication and control for a unified system from utility to home, including efficient building systems, home automation and smart appliances. A Smart Grid can provide a path to a predictive, self-healing grid, including demand management, allows management local generation, renewables, and storage

As implementation and architecture becomes more sophisticated, electricity meters demand additional processing power and larger flash memories for software stacks, and to support communication protocols and remote firmware updates.

Smart Meters also need a large number of serial communication ports to connect the different communication modules, such as RS-485, RS-232, IRda, PLC, GPRS, and RF.

Although electricity meters are powered by mains, they must be able to utilize battery power if current is cut, and during initial calibration. In these cases, the RTC must be running. Power consumption will be an increasing priority as plans proceed to install millions of Smart Meters globally.

Features and Benefits

Superior ADC performance, including:

High performance embedded 12 bit ADC, with 16-bit capability using over sampling
2.0 Mega samples/second at 12-bit resolution

Differential input channels, removing common mode noise for improved accuracy
Dual ADC (or dual sample and hold) allows simultaneous measurement of voltage and current

Integrated programmable gain, from 1X up to 64X, eliminates need for external gain stage and also eliminates possibility to tamper with external gain settings

Single-phase and poly-phase meters can be supported by increasing the number of ADC channels on the microcontroller.
Scalable microcontroller families support entry level meters up to AMI meters.
Large flash size supports a variety of communications protocols, including RF, PLC, and GSM.
Power-efficient solutions provide low power consumption, especially when operating from a battery.
Embedded RTC replaces external expensive RTC.
Multiple communication peripherals (UART, SPI) connect communication modules such as PLC, RF, IRda, RS-485, and SmartCard.
RF solutions compliant with industry standards.
Security solutions include AES, DES, RSA, ECC, SHA-256, RNG
High EMC performance reduces the need for external protection.
Best-in-class, easy to use development speed time to market.

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The measurement of energy used is undertaken by the metrology block. Depending on the required accuracy, this can be performed by the internal ADC embedded in the microcontroller, through various current and voltage sensors. Alternatively, measurement can be processed by an external component, either an ASIC or ADC.

Single and poly phase solutions can be implemented using the same techniques, with an increase in the number of current sensors and ADC channels required.

The display requirements can vary, sometimes using the embedded segment LCD controller in the microcontroller, or for flexibility, an LCD display with embedded "chip on glass" is used.

External non-volatile memory (NVM), shown in the block diagram is used for data logging and to facilitate remote firmware updates. NVM can also store calibration data for the metrology. Please note that most Atmel AVR microcontrollers embed EEPROM so an external component may not be required.

The communication modules are dependant on the metering infrastructure, and are available on the Atmel AMR and AMI architectures. The security Block enables authentication and encryption of communicated information.

Products

With its broad microcontroller portfolio, RF transceivers, NVM and Hardware Security products, Atmel offers the key components of an electricity meter. The AVR and ARM microcontroller families provide a rich array of features that electricity meters demand.

Microcontroller	NVM	Hardware Security	RF Transceivers
AVR UC3 ARM-Based Solutions: AT91SAM9M10 Series AT91SAM9G45 Series AT91SAM3S Series AT91SAM3U Series	DataFlash EPROM Parallel Flash Parallel EEPROM Serial EEPROM Serial Flash	Hardware Security Solutions	Single-chip (Microcontroller and Transceiver) Transceivers ZigBit Modules

Learn more about the Atmel solution Application Notes, Devices, and Tools and Software