STMicroelectronics Introduces Complete Electric Energy Meter Evaluation Board Integrating Low-Cost Sensors and Robust Galvanic Isolation

     STMicroelectronics' new energy meter evaluation board uses low-cost anti-galvanic shunt sensors and advanced galvanic isolation technology to achieve excellent reliability and robustness, speeding up the design of three-phase AC energy meters and meeting the most stringent energy meter quality in the world and precision standards.

     The EVALSTPM-3PHISO evaluation board integrates a high-accuracy STPMS2 metering front-end IC and an advanced STISO621 digital isolator, as well as customizable turnkey firmware running on an STM32 microcontroller for calculating metering and power quality data. The optimally designed sensing circuit and PCB layout ensure that the power meter has excellent robustness against EMI interference and an excellent signal-to-noise ratio for high-precision measurement and post-processing calculations.

     STPMS2 is a dual-channel 24-bit second-order sigma-delta modulator. It measures the voltage and current of each phase of AC through an on-board voltage divider and shunt sensor, and then oversamples the signal using a synchronous 4MHz clock assigned by the microcontroller, And uses multiplexing to transmit a sigma-delta bit stream of voltage and current through one output pin. A three-phase meter system requires three STPMS2s to collect voltage and current data for each phase.

     The meter firmware provided with the board utilizes the STM32 microcontroller's integrated sigma-delta modulation digital filter (DFSDM) to convert the six bit streams into 24-bit voltage and current values and calculates all metering data in real-time every 200µs. The firmware also implements a virtual communication port for accessing internal parameters, reading metering data, modifying internal configuration and calibrating the board.

     The STISO621 dual-channel digital isolator, the first in a new family of isolation ICs, uses ST's 6kV thick oxide galvanic isolation technology to transfer data between isolated domains, suitable for a variety of industrial applications. The STISO621 features two independent channels with Schmitt trigger inputs, ensuring high noise immunity and keeping pulse distortion below 3ns. The maximum data transmission rate of STISO621 reaches 100Mbit/s, the pulse withstand voltage (VIOTM) is up to 6000V, and the maximum repetitive isolation voltage (VIORM) is 1200V. Compared with traditional optical isolators, STISO621 ensures faster data transmission and longer service life. longer and more reliable.

     ST's energy meter evaluation boards comply with EN 50470-x, IEC 62053-2x, ANSI12.2x AC energy meter standards. The application provides broadband, fundamental, reactive and apparent power and energy data per phase or cumulative active energy or power; three-phase active/apparent power measurement accuracy class 0.5 and IEC 62053-21 three-phase reactive power measurement accuracy class 1, RMS calculation and THD distortion calculation (optional) for each voltage and current signal, and DC measurement, as well as line period, phase shift and phase voltage Latency measurement.