High-Accuracy Split-Phase CT Electricity Meter Reference Design Using Standalone ADCs
- TIDUEM8B March 2019 – February 2021

High-Accuracy Split-Phase CT Electricity Meter Reference Design Using Standalone ADCs

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IMPORTANT NOTICE

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DESIGN GUIDE

High-Accuracy Split-Phase CT Electricity Meter Reference Design Using Standalone ADCs

Description

This reference design implements Class 0.1 split-phase energy measurement using high-performance, multi-channel analog-to-digital converters (ADC). The ADC samples current transformers (CT) at 8 kHz to measure the current and voltage of each leg of the AC mains. The reference design achieves high accuracy across a wide input current range (0.05–100 A) and supports high sampling frequencies necessary for power quality features such as individual harmonic analysis. An ADC sample rate of 32 ksps can be acheived by disabling some software functions. Independent ADCs provide flexibility in the choice of metrology microcontrollers compared to integrated SoCs. This reference design uses a SimpleLink™ARM®Cortex®-M4 host microcontroller for metrology. The necessary software functionality is implemented in the ADC Energy Metrology library. The software library can be compiled with Code Composer Studio™ or IAR Embedded Workbench®.

Resources

TIDA-010037	Design Folder
ADS131M04, MSP432P4111	Product Folder
TPS3840, TPS25921l, THVD1500	Product Folder
ISO7731B, TRS3232E	Product Folder
ADC Energy Metrology Library	Software

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Features

Split-phase metrology for electricity meters that meets ANSI C12.20 Class 0.1 active energy accuracy requirements across 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 5-kV_RMS isolation
Communications module expansion with current limit and overvoltage and undervoltage protection
Tested across 50 mA to 100 A input range
High active energy accuracy still obtained when ADC sample rate increased to 32 ksps
Software for energy metrology and displaying results on a Windows® PC GUI.