How to reduce noise in I/O module AI/AO cabling?

Noise reduction for AI/AO analog signal routing in I/O modules requires attention to detail. Traces should be as short and straight as possible, avoiding crossing digital areas or above switching power supplies. Differential routing must be used, and pairs must be of equal length and spacing to suppress common-mode noise. A complete, unsegmented analog ground plane should be provided beneath the routing as a return current reference. Vias should be avoided in signal paths; if necessary, the reference ground planes on both sides of the via should be continuous. For multiple analog signals, increase the spacing between traces or use ground lines for isolation.

Power traces should be kept away from analog signal lines; if they cross, they must be perpendicular. Near the ADC/DAC chip, analog and digital power supplies should be isolated using ferrite beads, and sufficient decoupling capacitors should be installed. The shielding layer for analog signals should be grounded at a single point on the module to avoid ground loops. For high-frequency noise, a small-value ferrite bead, such as the PBZ1005 series, can be connected in series on the signal lines. After layout, an oscilloscope can be used to observe noise on the signal lines, and a spectrum analyzer can be used to locate the noise source for targeted optimization.