Today, the power industry faces ever-increasing customer
demand, straining systems across the globe. Even as the
industry takes further steps to ensure reliable service, providers can benefit from early-warning technology to prevent outages caused by excessive demand. In order for utility providers to better realise and test new technologies, the metering industry must turn to advanced integrated circuits (ICs) that are capable of making meters more accurate and reliable, and that incorporate automated meter reading (AMR).
Besides higher data accuracy and reliability, AMR-enabled energy meters offer lower customer service care cost and lower meter reading cost. E-meter manufacturers are rapidly upgrading their designs to implement new AMR technologies. By offering features such as data transmission over power line and remote communication via network, meter manufacturers can enable energy providers to detect, identify and resolve power outages remotely and expedite a solution.
Discerning customers will value receiving detailed individual information, increasing their trust in their bill’s credibility. Consumers can take advantage of cost incentives such as multi-rate billing or pre-pay energy with smart card prepayment. Adopting rate incentives can encourage customers to reduce peak usage, thereby leading to cleaner power distribution, fewer spikes in power generation and reduced need for more energy plants.
To meet the stringent requirements of advanced electronic energy meters, many manufacturers have relied on custom application-specific integrated circuits (ASIC) that offered mixed-signal solutions. ASICs can be expensive, requiring non-reoccurring engineering cost and extending both design and production lead-times. A better option is to use standard catalogue products that solve similar problems for multiple customers at a lower shared cost. These ‘application-specific standard products’ (ASSP) are excellent choices, since they offer high performance analog and low cost digital circuitry and reduce manufacturers’ time-to-market.
A Single-Chip IC for AMR E-Meters
An advanced electronic e-meter must contain circuitry that offers precision voltage and current conversion over a wide dynamic range, a programmable Flash microprocessor, non-volatile storage, a real-time clock function, flexible display and AMR-enabled communication features. The world’s most advanced single-chip Flash microcontroller unit (MCU) for energy metering, the MSP430FE42x family by Texas Instruments, was created to meet this demand. The family offers high performance analog, low cost digital logic and an embedded Flash microprocessor as a complete system-on-chip metering solution. In addition, the family provides fail-safe modes that enable shut down and communication features that can forewarn utility providers of a problem.
This single-chip Flash MCU provides greater flexibility for designers to focus on developing feature-rich programmable functions, instead of developing custom ASIC hardware. The combination of an energy measurement module with high performance analog-to-digital converters (ADC) and a fully programmable MCU in one IC lowers manufacturing cost, shortens design cycles, increases accuracy and extends flexibility.
The intelligence of the mixed signal MSP430FE42x ‘e-meter chip’ lies in an embedded signal processor (ESP) that performs the essential metrology functions. This preprogrammed ESP contains three 16-bit independent sigma delta ADCs and three programmable gain amplifiers. The 16-bit ESP multiplies current and voltage continuously to derive power consumption. While the ESP is managing the signal conditioning and power calculation, the main central processing unit gains full access to 32kB of in-system programmable (ISP) Flash and 1kB RAM for unique application features. External non-volatile memory traditionally used for calibration and unit identification serial numbers can be eliminated and instead saved in normal Flash. When needed, energy consumption data can also be recorded in the ISP Flash.
With industry standard peripherals such as an integrated 128-segments LCD driver, an enhanced watchdog timer, serial communication interface, brownout protection and supply voltage supervisor, the MSPFE42x is equipped to provide highly accurate energy measurement, simplify the manufacturing process and improve long-term meter reliability. Fewer ICs mean increased reliability, since there is less exposure to potential failures in the field.
The MSP430FE42x requires only a single low-frequency 32kHz crystal to perform the real-time clock function and enable an ultra-low power standby mode in a power outage situation. The high speed system clock is digitally generated on-chip, independent of the crystal, and in the possible event of a crystal failure it switches to a failsafe mode to allow the MCU to keep processing at a minimum level.
Meter designers can now employ a single IC that uses high performance analog and an embedded MCU to implement feature-rich AMR energy meters, offering energy providers and consumers more reliable information and better service.