High-Accuracy Split-Phase CT Fuel Gauge Reference Design Using Standalone ADC

This reference design implements Class 0.1 split-phase energy metering using a high-performance, multi-channel analog-to-digital converter (ADC). An independent ADC samples the current transformer (CT) output at 8kHz and measures the current and voltage at each branch of the main AC power supply. The reference design achieves high accuracy over a wide input current range (0.05 – 100 amps) and supports high sampling frequencies when necessary to enable advanced power quality features such as independent harmonic analysis. Using a stand-alone ADC to sample the CT output gives designers more flexibility in selecting a metrology microcontroller than an integrated SoC and application-specific dedicated products. This reference design uses the SimpleLink™ ARM Cortex-M4 host microcontroller to calculate energy metering parameters. The design can also use an ADC sampling rate of 32ksps by enabling only a subset of the total energy measurement parameters.

characteristic

• ● The fuel meter uses split-phase measurement and meets the ANSI C12.20 Class 0.1 active energy accuracy requirements of the 10000:1 input range.
• ● Active and reactive energy and power, root mean square (RMS) current and voltage, power factor and line frequency calculations
• ● Isolated RS-232 and RS-485 with 5kV RMS isolation
• ● Communication module expansion with current limitation and overvoltage and undervoltage protection
• ● Tested over 50mA to 100A input range
• ● Complete, tested reference design with hardware documentation and design guide
• ● When the ADC sampling rate is increased to 32ksps, high active energy accuracy can still be obtained