ST is aiming at compliant 3 phase watt meters with an evaluation kit built around the STPMS2 double channel 24bit second-order ΣΔ modulator.
Called EVALSTPM-3PHISO, it measures through a voltage divider and current shunt for each phase. “Sensing circuitry and PCB layout are optimised to maximise signal-to-noise ratio for accuracy,” said the company. The STPMS2 oversamples signals using a 4MHz clock and outputs voltage and current sigma-delta bit-streams, multiplexed on the same pin.”
6kV galvanic isolation (up to 100Mbit/s and <3ns distortion) between ADC and host microcontroller is provided by the company’s STISO621W chip, which uses inductive transfer internally. Measurement bandwidth is 5kHz. Creepage and clearance are 8mm.
Accuracy is Class 0.5 according to IEC 62053-22 on 3-ph active-apparent power measurement and Class 1 to IEC 62053-21 on 3-phase reactive power.
The EVALSTPM-3PHISO product page is here. Brevity is taken too seriously in the associated data brief – fingers crossed for more in Rev 2 as the shunts look interesting.
Source: electronicsweekly
