AC Coupling

AC coupling is the connection of a signal from one circuit to another in a manner that rejects DC components.

The signal acquired from the sensor consists of both DC and AC components, where the DC portion offsets the AC portion from zero. In an analog system, simple AC coupling removes the DC offset in the system by means of a capacitor in series with the signal. An AC-coupled sensor system attenuates voltage offset due to constant current excitation.

AC coupling also attenuates the long-term DC drift that sensors have due to age and temperature effect. When implemented in hardware, AC coupling can prevent the saturation of an input channel and can enable the use of a more narrow input range to improve AC amplitude resolution and usable dynamic range of the channel. When implemented in software, AC coupling can remove erroneous DC data that would otherwise invalidate signal processing such as integration and measurement results such as RMS and Peak levels.