How to prevent latency in I/O module AI filtering?

To achieve analog input filtering for I/O modules without introducing significant delay, it's necessary to select filters with linear phase characteristics or employ predictive compensation techniques. For fixed-frequency noise, such as power frequency interference, IIR digital filters with steep stopbands can be used, and the group delay caused by their nonlinear phase can be corrected using phase compensation algorithms. In hardware, passive RC first-order filters introduce the least delay, with their group delay remaining essentially constant within the passband. For multi-order filtering, Bessel filters have the flattest group delay characteristics; although their amplitude-frequency roll-off is slower, they minimize phase distortion.

In high-speed data acquisition systems, FIR digital filters can be used; by designing linear-phase filter coefficients, consistent delay across all frequency components can be ensured. Another approach is to use synchronous sampling techniques. For example, to suppress 50Hz power frequency interference, the sampling frequency can be set to an integer multiple of the power frequency, and then averaged over multiple cycles, without introducing additional signal delay. During the design process, filter simulations should be performed in Matlab or Python to comprehensively evaluate their amplitude-frequency, phase-frequency characteristics, and response time to step signals.