Coupling between two AI channels - NI Discussion Forums

Coupling between two AI channels - NI Discussion Forums: "2) Channel-to-channel settling crosstalk: signals on one channel influence the measurement on the next channel in the scan sequence. When the multiplexer switches from one signal to the next, the signal at the A/D converter does not switch instantaneously from one to the other. Due to limited bandwidth of the amplifier and the A/D converter, and capacitance in the multiplexers, there is a settling time as the signal transitions from one level to the next. At first blush it usually has the shape of an exponential function, though once that part has settled out there's usually slower effects that aren't exponential. Those slower components of the settling curve are often due to thermal transients and dielectric absorption in capacitors. In any case, if the A/D converter samples the signal before it's through settling adequately to the new level, the new signal will carry some residual influence of the previous channel. Since the curve usually decreases monotonically, waiting longer to settle decreases the amount of influence. So one thing to try is to lower the channel-to-channel sample rate within each scan - if that decreases the noise, then your problem is likely related to settling."

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