How to filter out analog AI differential modes in I/O modules?

Filtering differential-mode interference at the analog inputs of I/O modules primarily targets noise superimposed on the useful signal. A fundamental method is to use a passive RC or LC low-pass filter at the signal input, with a cutoff frequency slightly higher than the highest signal frequency to preserve the signal and filter out high-frequency noise. For low-frequency power line interference, a dual-T active filter with notch characteristics can be used. In systems using ADC sampling, utilizing an anti-aliasing filter at the front end is crucial to prevent high-frequency noise from aliasing into the low-frequency band. For high-precision measurements, multi-stage switched-capacitor filters or digital filters can be used for post-processing. When wiring, analog signal lines should use twisted-pair cables and be kept away from noise sources. Power supply decoupling must be adequate to prevent power supply noise from coupling to the signal path through the amplifier. The grounding terminals of all filters must be connected to a clean analog ground. It is important to note that the introduction of filters introduces phase delay and amplitude attenuation, requiring compensation or calibration at the system level. Observing the signal spectrum using a spectrum analyzer can identify noise components, allowing for the design of targeted filters.