Ultra-low-power microcontroller family brings accuracy, low power to three-phase metering
By Margery Conner, Technical Editor -- EDN, July 2, 2009
Accurate, low power, and tamper proof are the key features of the new generation of smart meters that will enable the infrastructure of the smart grid. Targeting that market, Texas Instruments has added the MSP430F471xx to its 430 family of ultra-low-power microcontrollers for smart-power-meter applications. The device has accuracy better than 0.1% and a dynamic range of 2400 to 1, necessary for the wide range of high and low currents that power meters encounter. Current electromechanical meters, in contrast, have only about 2% accuracy. Low-power operation is important for electronic power meters because they must run on a battery-backup power during outages. Although these outages are relatively infrequent in the United States, extended outages can occur weekly in developing parts of the world.
In its low-power mode, the 471xx can keep an LCD and a real-time clock alive for continued metering and reporting. Six sigma-delta ADCs monitor the three power phases, and a seventh monitors the ground return to see whether the equipment is drawing power or even if someone has tampered with the magnetic pickup. The device has multiple interfaces, including PLC (power-line communications) to communicate with the utility, and an RF interface for advanced meter infrastructure that allows in-home wireless-network communication. The device can have as much as 120 kbytes of flash memory and 8 kbytes of RAM. The chip sells for $5.75 to $7.95 (1000).
