[Answer] What Does Coupling Include? Methods and Types of Coupling

[Answer] What Does Coupling Include? Methods and Types of Coupling?

When using an oscilloscope or performing data acquisition, you will often encounter the concepts of AC coupling and DC coupling. Simply put, the signals we acquire are never perfectly ideal waveforms. For example, when acquiring an AC signal, a DC component may be mixed in; likewise, when acquiring a DC signal, an AC component may also be present.

To filter out the DC portion of a signal, AC coupling is used. AC coupling means inserting a capacitor between the signal and the acquisition point. Because a capacitor allows AC to pass while blocking DC, the DC component can be filtered out easily. For this reason, AC coupling is also called capacitive coupling.

However, AC components generally cannot be removed in this way. Therefore, so-called DC coupling means that no processing is applied to the signal. This allows both AC and DC components to be acquired and analyzed at the same time.

If you want to filter out the AC component of a signal, you can consider using a filter. A low-pass filter can effectively remove a significant portion of the AC component.

DC coupling allows any type of signal to pass.

AC coupling allows only AC signals to pass.

To obtain an AC-coupled signal using an NI DAQ (data acquisition) device, you can insert a capacitor in series between the positive signal lead and the positive analog input channel on the DAQ device. Connect the negative signal lead directly to the corresponding negative analog input channel. This method removes the DC component from the signal, and the resulting AC signal is centered around 0 V. For more detailed information, please refer to the figure below.