Relationship between analog signal accuracy and EMC of I/O module

The analog accuracy of I/O modules is closely related to their EMC performance, as electromagnetic interference directly causes measurement errors. Common-mode interference raises the signal ground potential beyond the amplifier's common-mode input range, leading to output distortion. Differential-mode noise is directly superimposed on the useful signal, contributing to errors after ADC sampling. High-frequency interference can cause nonlinear responses in amplifiers or ADCs, and even latch-up effects. Power supply noise can couple into the signal path through devices with limited power supply rejection ratios (PSRR).

Therefore, high-precision analog circuits must have excellent EMC design. This includes using instrumentation amplifiers with high PSRR, low-noise power supplies and reference sources, effective filtering and shielding, and good grounding and layout to minimize various couplings. In EMC testing, such as EFT and surge testing, it is important not only to focus on functional compliance but also to monitor key accuracy metrics such as zero-point drift and full-scale error within acceptable limits. Conversely, good accuracy design itself, such as using low-temperature drift devices, low-noise op-amps, and adequate decoupling, helps improve immunity to certain types of noise. The design goal is to ensure that accuracy specifications still meet datasheet requirements under the most demanding EMC testing environments.