Application board implements 3-phase energy meter

The board is in stock at distributor Digi-Key Electronics.

The EVALSTPM-3PHISO evaluation board implements a complete 3-phase energy meter with low-cost shunt current sensors.

Based on the STPMS2 device, a dual-channel, 24-bit second order sigma-delta modulator, this solution measures voltage and current for each phase through a voltage divider and a shunt current sensor.

Sensing circuitry and PCB layout are optimised to maximise signal-to-noise ratio for optimal accuracy.

The STPMS2 oversamples the signal using a 4 MHz clock distributed in a synchronized way by the microcontroller and outputs voltage and current sigma-delta bitstreams, multiplexed on the same pin.

The two-wire communication between the STPMS2 modulator and the MCU is isolated by STISO621W, 6 kV galvanic isolated dual-channel bidirectional interface, allowing up to 100 Mbps rate and low pulse distortion (<3 ns) for safe and fast data transfer between isolated domains.

The FW embedded in the solution exploits the DFSDM filters of the STM32F413RH to convert the six bitstreams into 24-bits voltage and current data at a 200 µs rate.

All the metrology parameters are computed in real-time on a 200 µs basis.

Two LEDs are available for active and reactive pulses generation.

The FW also implements a virtual com port communication to easily access the internal parameters to read metrology data, modify the internal configuration for high flexibility of the application, and calibrate the board.