How to ensure isolation between I/O module channels?

To ensure isolation between I/O module channels and prevent mutual interference, both circuit design and structural implementation are crucial. Circuit-wise, each channel should have independent signal conditioning, sampling, and conversion circuitry, switched to a common ADC using a multiplexer or analog switch. However, attention must be paid to the potential impact of leakage current and charge injection from the switches on isolation. A more thorough approach is to use an independent isolation amplifier or ADC for each channel, with its digital output aggregated through a digital isolator. Structurally, for high-voltage or high-precision requirements, independent modular channels with independent shielding can be used.

On the PCB, analog traces between different channels should maintain sufficient distance or be isolated using ground lines. Power supplies should provide independent isolated power to each channel or group of channels, or at least through ferrite beads. For digital isolation, ensure complete separation of ground planes on both sides of the isolation barrier. During testing, interference signals can be injected into one channel to measure its impact on adjacent channels—a channel crosstalk test—to verify isolation. In software, channel polling sampling can be implemented with a dead time to avoid the effects of switching transients.