How to solve the mutual interference problem in multi-circuit measurements of an electrical force measurement switch (PMS)?

When a PMS performs simultaneous multi-loop (e.g., three-phase voltage and current) measurements, mutual interference may occur between loops through common ground impedance, spatial coupling, or power supply coupling, manifesting as fluctuations in readings of other loops due to load changes in one loop.

Solutions include: electrical isolation, independent references, and software compensation.

Electrical isolation: Use an independent ADC or isolation amplifier (e.g., ADuM7701) for each measurement to isolate the signal from the processing circuitry.

Independent reference: Each sampling circuit uses an independent reference voltage source and analog power supply, isolated by a PBZ1608E600Z0T ferrite bead. On the PCB layout, physically separate the sampling, amplification, and filtering areas of each loop, using ground isolation strips in between.

Spatial coupling suppression: Maintain sufficient spacing when installing each phase CT/VT, and use independent shielded cables for the output lines.

On the software side, synchronous sampling technology can be used to capture all loop signals simultaneously, avoiding computational mutual interference caused by time misalignment; digital filtering and cross-interference compensation algorithms can be applied to the sampled data. These measures can reduce the mutual interference error between multi-loop measurements from 2% to below 0.1%, meeting the requirements for accurate measurement of three-phase imbalance.