How to eliminate mutual interference from multiple sampling channels in a concentrator?

When a concentrator simultaneously samples multiple channels (such as three-phase voltage and current), mutual interference may occur between the loops through common ground impedance, spatial coupling, or power supply coupling. Eliminating mutual interference requires electrical isolation, independent references, and software compensation.

Electrical isolation: Use an independent ADC or isolation amplifier (such as ADuM7701) for each sampling channel.

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, the sampling, amplification, and filtering areas of each loop are physically separated, with ground isolation strips in between.

Spatial coupling suppression: Maintain spacing between phase CTs/VTs during installation, and use independent shielded cables for output lines. On the software side, employ synchronous sampling technology to sample all loop signals simultaneously, avoiding time misalignment; perform digital filtering and cross-interference compensation algorithms on the sampled data.

These measures can reduce the mutual interference error of multi-channel sampling from 2% to below 0.1%.