By today's technological standards, the common electromechanical energy meter is a relic of the past – incapable of anything but flat-rate pricing and infrequent meter readings.
Smart meters go well beyond the rudimentary functions of a basic electrical meter. Above all, the distinguishing quality of a smart meter is to support 2-way communication with utility providers. This is the key that opens the door to all other "smart" functions and the benefits thereof. Smart meters can provide support for remote diagnostics, dynamic pricing, tamper notification, consumption analysis, and more.
What does this mean for utility customers? For one, it creates something that has not existed since the grid's creation: an informed consumer base. People can analyze their own energy usage in as much detail as desired and then adjust the amount, manner, and time in which high load devices are used. Even today, most consumers are unaware that for utility providers, the cost of a kWh is greater during times of peak demand – after all, electricity is traditionally billed at a flat rate. By offering dynamic pricing based on real-time energy demand, electric companies create opportunities for customers to significantly lower their energy bill with simple changes, such as using the clothes dryer at off-peak hours. Also, these kinds of changes have the effect of reducing or "shaving" the demand peaks over the course of a day, which can further reduce energy costs.
In a two-chip solution, the essential metrology functions of the device are implemented as a separate functional unit, i.e. an energy meter IC. There are many possible reasons for choosing this architecture; for instance, the metrology firmware may require isolation and specific qualifications. Active power is sensed with a current transformer, commonly a Rogowski coil, which then provides the energy meter IC with analog power measurements. Typically, delta-sigma ADCs (analog-to-digital converters) within the energy meter chip perform the A/D conversion. The chip also tracks energy consumption, transmitting the data to the application processor, and possibly provides additional functions such as pre-amplification and tamper detection.
The application processor provides the substantial amount of non-volatile memory, processing power, and connectivity options needed to implement most of the smart meter's "smart" functions, such as consumption analysis, dynamic pricing, and other demand response features. All smart meters are capable of 2-way communication with a utility company, whether it is via power line communication (PLC), Zigbee wireless mesh networks, RS-485, or some combination of communications technologies. Choice of communications channel(s) and meter reading method are often dictated by cost, which depends largely on pre-existing infrastructure and the local regulations of a given region.
Major subsystems include:
- Application Processor
- Sensing and metrology: current and voltage sensors, energy meter IC
- Power management: offline AC/DC converter, voltage regulator, battery management system
- AMR-enabled communications: PLC modem, Zigbee, RS-485, etc.